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101.
Yang Shen Ioanna Kalograiaki Alessio Prunotto Matthew Dunne Samy Boulos Nicholas M. I. Taylor Eric T. Sumrall Marcel R. Eugster Rebecca Martin Alicia Julian-Rodero Benjamin Gerber Petr G. Leiman Margarita Menndez Matteo Dal Peraro Francisco Javier Caada Martin J. Loessner 《Chemical science》2021,12(2):576
Endolysins are bacteriophage-encoded peptidoglycan hydrolases targeting the cell wall of host bacteria via their cell wall-binding domains (CBDs). The molecular basis for selective recognition of surface carbohydrate ligands by CBDs remains elusive. Here, we describe, in atomic detail, the interaction between the Listeria phage endolysin domain CBD500 and its cell wall teichoic acid (WTA) ligands. We show that 3′O-acetylated GlcNAc residues integrated into the WTA polymer chain are the key epitope recognized by a CBD binding cavity located at the interface of tandem copies of beta-barrel, pseudo-symmetric SH3b-like repeats. This cavity consists of multiple aromatic residues making extensive interactions with two GlcNAc acetyl groups via hydrogen bonds and van der Waals contacts, while permitting the docking of the diastereomorphic ligands. Our multidisciplinary approach tackled an extremely challenging protein–glycopolymer complex and delineated a previously unknown recognition mechanism by which a phage endolysin specifically recognizes and targets WTA, suggesting an adaptable model for regulation of endolysin specificity.Combining genetic, biochemical and computational approaches, we elucidated the molecular mechanisms underlying the recognition of Listeria wall teichoic acid by bacteriophage-encoded SH3b repeats. 相似文献
102.
Mei Y Wu T Xu C Langenbach KJ Elliott JT Vogt BD Beers KL Amis EJ Washburn NR 《Langmuir : the ACS journal of surfaces and colloids》2005,21(26):12309-12314
A simple yet versatile method was developed to prepare a low-density polymerization initiator gradient, which was combined with surface-initiated atom transfer radical polymerization (ATRP) to produce a well-defined poly(2-hydroxyethyl methacrylate) (HEMA) gradient substrate. A smooth variation in film thickness was measured across the gradient, ranging from 20 A to over 80 A, but we observed a nonmonotonic variation in water contact angle. Fits of X-ray reflectivity profiles suggested that at the low graft density end, the polymer chain structure was in a "mushroom" regime, while the polymer chains at high graft density were in a "brush" regime. It was found that the "mushroom" region of the gradient could be made adhesive to cells by adsorbing adhesion proteins, and cell adhesion could be tuned by controlling the density of the polymer grafts. Fibroblasts were seeded on gradients precoated with fibronectin to test cellular responses to this novel substrate, but it was found that cell adhesion did not follow the expected trend; instead, saturated cell adhesion and spreading was found at the low grafting density region. 相似文献
103.
Philippe Hennig Eric Raimbaud Christophe Thurieau Jean-Paul Volland André Michel Jean-Luc Fauchère 《Journal of computer-aided molecular design》1996,10(1):83-86
Summary The conformation in dimethylsulfoxide of the somatostatin derivative angiopeptin and of three disulfide-free analogs was estimated by two-dimensional nuclear magnetic resonance spectroscopy at room temperature. The resulting 3D molecular graphics were compared and shown to reflect the observed differences in the inhibition of restenosis after rat aorta balloon injury by these octapeptide inhibitors. Angiopeptin and its active analog 2 displayed a relatively rigid conformation of the cyclic hexapeptide backbone due to the presence of two well-defined hydrogen bonds, further stabilized by a third hydrogen bond outside the ring. No such constraints were detected for the two biologically inactive analogs, which, compared to 2, had a two-atom longer or shorter hexapeptide ring. The well-defined structure of compound 2 may serve as an improved pharmacophore for this new class of drugs. 相似文献
104.
Wang TT Chung SM Wu FI Shu CF Diau EW 《The journal of physical chemistry. B》2005,109(50):23827-23835
We performed time-resolved spectral investigations of two distyrylcarbazole derivatives, 2,7- and 3,6-distyrylcarbazole (2,7-DPVTCz and 3,6-DPVTCz, respectively), in dilute toluene solution and in solid films mixed with poly(methyl methacrylate) (PMMA). The lifetime of 2,7-DPVTCz in its excited state in solution is approximately 100 times as great as that of 3,6-DPVTCz, consistent with their photophysical nature. The former shows intense emission, but the latter is nearly nonfluorescent in a free environment. Moreover, the lifetime of 3,6-DPVTCz in its excited state increased also approximately 100 times when the molecule was encapsulated in a 3,6-DPVTCz/PMMA solid film, indicating that intramolecular motion of the molecule significantly affects the observed relaxation dynamics in a confined environment. Calculations on the excited states indicate that an efficient intersystem crossing is activated upon twisting of the bridged C-C single bond in a free 3,6-linked carbazole; such efficient deactivation is impractical in 2,7-linked carbazole or for 3,6-linked carbazole in a PMMA matrix. Information obtained from experiments on femtosecond fluorescence enables us to distinguish crucial relaxation processes in the excited state for a profound understanding of the details of vibrational and electronic relaxations of 3,6-DPVTCz in solution. 相似文献
105.
Multiphoton laser scanning microscopy offers advantages in depth of penetration into intact samples over other optical sectioning techniques. To achieve these advantages it is necessary to detect the emitted light without spatial filtering. In this nondescanned (nonconfocal) approach, ambient room light can easily contaminate the signal, forcing experiments to be performed in absolute darkness. For multiphoton microscope systems employing mode-locked lasers, signal processing can be used to reduce such problems by taking advantage of the pulsed characteristics of such lasers. Specifically, by recovering fluorescence generated at the mode-locked frequency, interference from stray light and other ambient noise sources can be significantly reduced. This technology can be adapted to existing microscopes by inserting demodulation circuitry between the detector and data collection system. The improvement in signal-to-noise ratio afforded by this approach yields a more robust microscope system and opens the possibility of moving multiphoton microscopy from the research lab to more demanding settings, such as the clinic. 相似文献
106.
Eric Séré 《Communications in Mathematical Physics》1995,172(2):293-316
Consider a smooth Hamiltonian system in 2N
,
, the energy surface ={x/H(x)=H(0)} being compact, and 0 being a hyperbolic equilibrium. We assume, moreover, that {0} is of restricted contact type. These conditions are symplectically invariant. By a variational method, we prove the existence of an orbit homoclinic, i.e. non-constant and doubly asymptotic, to 0. 相似文献
107.
Logarithmic correction to the probability of capture for dissipatively perturbed Hamiltonian systems
Hamiltonian systems are analyzed with a double homoclinic orbit connecting a saddle to itself. Competing centers exist. A small dissipative perturbation causes the stable and unstable manifolds of the saddle point to break apart. The stable manifolds of the saddle point are the boundaries of the basin of attraction for the competing attractors. With small dissipation, the boundaries of the basins of attraction are known to be tightly wound and spiral-like. Small changes in the initial condition can alter the equilibrium to which the solution is attracted. Near the unperturbed homoclinic orbit, the boundary of the basin of attraction consists of a large sequence of nearly homoclinic orbits surrounded by close approaches to the saddle point. The slow passage through an unperturbed homoclinic orbit (separatrix) is determined by the change in the value of the Hamiltonian from one saddle approach to the next. The probability of capture can be asymptotically approximated using this change in the Hamiltonian. The well-known leading-order change of the Hamiltonian from one saddle approach to the next is due to the effect of the perturbation on the homoclinic orbit. A logarithmic correction to this change of the Hamiltonian is shown to be due to the effect of the perturbation on the saddle point itself. It is shown that the probability of capture can be significantly altered from the well-known leading-order probability for Hamiltonian systems with double homoclinic orbits of the twisted type, an example of which is the Hamiltonian system corresponding to primary resonance. Numerical integration of the perturbed Hamiltonian system is used to verify the accuracy of the analytic formulas for the change in the Hamiltonian from one saddle approach to the next. (c) 1995 American Institute of Physics. 相似文献
108.
We analyze the analytic continuation of the formally divergent one-loop amplitude for scattering of the gravitonmultiplet in the Type II superstring. In particular we obtain explicit double and single dispersion relations, formulas for all the successive branch cuts extending out to +, as well as for the decay rate of a massive string state of arbitrary mass2N into two string states of lower mass. We compare our results with the box diagram in a superposition of 3-like field theories. The stringy effects are traced to a convergence problem in this superposition.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 98. No. 3, pp. 442–455, March, 1994. 相似文献
109.
Zachary Yoder Daniela Macari Gavriel Kleinwaks Ingemar Schmidt Eric Acome Christoph Keplinger 《Advanced functional materials》2023,33(3):2209080
Soft robotic grippers achieve increased versatility and reduced complexity through intelligence embodied in their flexible and conformal structures. The most widely used soft grippers are pneumatically driven; they are simple and effective but require bulky air compressors that limit their application space and external sensors or computationally expensive vision systems for pick verification. In this study, a multi-material architecture for self-sensing electrohydraulic bending actuators is presented that enables a new class of highly versatile and reconfigurable soft grippers that are electrically driven and feature capacitive pick verification and object size detection. These electrohydraulic grippers are fast (step input results in finger closure in 50 ms), draw low power (6.5 mW per finger to hold grasp), and can pick a wide variety of objects with simple binary electrical control. Integrated high-voltage driving electronics are presented that greatly increase the application space of the grippers and make them readily compatible with commercially available robotic arms. 相似文献
110.
Hengfei Gu Fei Zhang Shinjae Hwang Anders B. Laursen Xin Liu So Yeon Park Mengjin Yang Rosemary C. Bramante Hussein Hijazi Leila Kasaei Leonard C. Feldman Yao-Wen Yeh Philip E. Batson Bryon W. Larson Mengjun Li Yifei Li Keenan Wyatt James L. Young Krishani Teeluck Kai Zhu Eric Garfunkel G. Charles Dismukes 《Advanced functional materials》2023,33(25):2301196
The rapidly increasing solar conversion efficiency (PCE) of hybrid organic–inorganic perovskite (HOIP) thin-film semiconductors has triggered interest in their use for direct solar-driven water splitting to produce hydrogen. However, application of these low-cost, electronic-structure-tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic-catalyst-electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n+silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high-temperature annealing of the catalyst/TiO2-protected-n+silicon interface necessary to retard electrolytic corrosion. Halide composition is examined in the (FA1-xCsx)PbI3 system with a bandgap suitable for tandem operation. A fill factor of 72.5% is achieved using a Spiro-OMeTAD-hole-transport-layer (HTL)-based HOIP/n+Si solar cell, and a high photocurrent density of −15.9 mA cm−2 (at 0 V vs reversible hydrogen electrode) is attained for the HOIP/n+Si/Pt photocathode in 1 m NaOH under simulated 1-sun illumination. While this thin-film design creates stable interfaces, the intrinsic photo- and electro-degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices. 相似文献