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1.
Whereas glucose oxidase and related proteins are encapsulated readily in silica sol–gels, α-hydroxy enzymes such as lactate
oxidase (LOx), are reported to be damaged by electrostatic interaction with these matrices. Based on a previous report, poly(ethyleneimine),
PEI, was evaluated as a protecting compound under conditions suited to analytical measurements. With LOx and PEI co-encapsulated
in a silica sol–gel, the enzyme retained 62% of its initial activity after 20 days. In the absence of PEI, activity was lost
during the processing. Batch analytical measurements with enzyme-doped sol–gel yielded a linear response over the range 0.5–2.0 mM
lactate and a detection limit of 0.03 mM lactate. Both simple incorporation of LOx in a silica sol–gel and an alternative
protection method, blocking the ion-exchange sites on silica with La(III), failed. These negative results supported the hypothesis
that the efficacy of PEI was related to its formation of a protective sheath around the enzyme.
Author for correspondence. E-mail: coxja@muohio.edu
Received July 29, 2002; accepted December 15, 2002
Published online May 19, 2003 相似文献
2.
Gibson SE Kaufmann KA Loch JA Steed JW White AJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(8):2566-2576
Understanding the interaction of chiral ligands, alkynes, and alkenes with cobaltcarbonyl sources is critical to learning more about the mechanism of the catalytic, asymmetric Pauson-Khand reaction. We have successfully characterized complexes of the type [Co2(alkyne)(binap)(CO)4] (BINAP=(1,1'-binaphthalene)-2,2'-diylbis(diphenylphosphine)) and shown that diastereomer interconversion occurs under Pauson-Khand reaction conditions when alkyne=HC[triple bond]CCO2Me. Attempts to isolate [Co2(alkyne)(binap)(CO)x] complexes with coordinated alkenes led to the formation of cobaltacyclopentadiene species. 相似文献
3.
Loch RA Dubrouil A Sobierajski R Descamps D Fabre B Lidon P van de Kruijs RW Boekhout F Gullikson E Gaudin J Louis E Bijkerk F Mével E Petit S Constant E Mairesse Y 《Optics letters》2011,36(17):3386-3388
We characterize the phase shift induced by reflection on a multilayer mirror in the extreme UV range (80-93?eV) using two techniques: one based on high order harmonic generation and attosecond metrology (reconstruction of attosecond beating by interference of two-photon transitions), and a second based on synchrotron radiation and measurements of standing waves (total electron yield). We find an excellent agreement between the results from the two measurements and a flat group delay shift (±40?as) over the main reflectivity peak of the mirror. 相似文献
4.
5.
Covalent side-chain cross-linking has been shown to be a viable strategy to control peptide folding. We report here that an oxime side-chain linkage can elicit α-helical folds from peptides in aqueous solution. The bio-orthogonal bridge is formed rapidly under neutral buffered conditions, and the resulting cyclic oximes are capable of dynamic covalent exchange. 相似文献
6.
Andreev A Lévy A Ceccotti T Thaury C Platonov K Loch RA Martin P 《Physical review letters》2008,101(15):155002
Recent significant improvements of the contrast ratio of chirped pulse amplified pulses allows us to extend the applicability domain of laser accelerated protons to very thin targets. In this framework, we propose an analytical model particularly suitable to reproducing ion laser acceleration experiments using high intensity and ultrahigh contrast pulses. The model is based on a self-consistent solution of the Poisson equation using an adiabatic approximation for laser generated fast electrons which allows one to find the target thickness maximizing the maximum proton (and ion) energies and population as a function of the laser parameters. Model furnished values show a good agreement with experimental data and 2D particle-in-cell simulation results. 相似文献
7.
Dorier J.-L. Gindrat M. Hollenstein C. Salito A. Loch M. Barbezat G. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2001,29(3):494-501
The fluctuating behavior of a Sulzer Metco F4 DC plasma gun has been investigated by simultaneous measurement of the time dependencies of the are voltage and of images from the nozzle interior. An end-on imaging arrangement using a mirror and a mask in the optical path from the are to the camera allows visualization of the anodic arc attachment by strongly attenuating the bright emission from the are column. With the torch operating in the restrike mode, sequences of images have been acquired in synchronization with several typical features of the are voltage fluctuations showing that the attachment nature changes during a restrike cycle. Multiple attachments which coexist at least during the 1 μs exposure time of the camera have been evidenced and are interpreted as a continuous process of creation/vanishing of successive arc roots with a smooth transfer of the current from one to the other. The anode wear is shown to have a strong effect on the root position over the anode periphery, with a preference for attachment in eroded regions. The effects of operation parameters such as current, gas flow and injector type on the attachment nature and position are also presented 相似文献
8.
This paper presents the results of an investigation evaluating the forces present in a statically loaded bicycle chain prior
to and beyond sprocket engagement. Comparisons are made with previous investigations that have been limited to industrial
chains and sprockets. The chain drive system for a bicycle differs from the industrial standard types not only in its size
but in its operation. A high degree of lateral flexibility is required in the bicycle chain for it to operate with noncoplanar
sprockets having an effective misalignment of 3 deg or more. The experimental analysis in this paper considers chain loads
for a range of sprocket sizes and angles of misalignment. Results indicate that localized bending arising from misalignment
between chain and sprocket can increase or decrease the strain on the side plates by a substantial fraction of the direct
strain due to chain tension. The work presented here is part of a more general study of bicycle chain efficiency for competition
applications. 相似文献
9.
Robert H. Crabtree Jennifer A. Loch Karin Gruet Dong-Heon Lee Cornelia Borgmann 《Journal of organometallic chemistry》2000,600(1-2):7-11
In a biomimetic approach to organometallic catalysis, pendant hydrogen-bonding groups are shown to influence the chemistry of ligand binding and activation in an iridium complex. Such groups can bind a substrate by hydrogen bonding and so offer the possibility of a biomimetic approach to catalysis where binding is controlled via molecular recognition. Because catalyst design in this area may be challenging, combinatorial and rapid screening methods may be needed to assay potential catalysts and initial progress on developing these methods for hydrosilation of alkenes and imines is described. Catalysis of aldehyde imination and the origin of pKa changes of bound H2 are discussed. 相似文献
10.
R. A. Loch A. Lévy T. Ceccotti F. Quéré C. Thaury H. George F. Bijkerk K.-J. Boller Ph. Martin 《The European physical journal. Special topics》2009,175(1):133-138
Enhanced backward-acceleration of ions is experimentally observed when ultra-short, high-intensity and ultra-high-contrast
laser pulses interact with thin foils having thicknesses in the order of the penetration depth of the laser light. Below the
experimentally observed optimum foil thickness for the maximum ion energy versus thickness, there arises a second peak. 1D
simulations on foils with an initial plasma density gradient show a similar trend as the experiment. It appears that in this
regime of extremely thin foils it is important to take into account the limited expansion of the plasma that is formed by
ultra-high-contrast pulses. 相似文献