Guiding neutral atoms on a chip

We demonstrate the guiding of neutral atoms by the magnetic fields due to microfabricated current-carrying wires on a chip. Atoms are guided along a magnetic field minimum parallel to and above the current-carrying wires. Two guide configurations are demonstrated: one using two wires with an external magnetic field, and a second using four wires without an external field. These guide geometries can be extended to integrated atom optics circuits, including beam splitters.     

Polymyxin-coated Au and carbon nanotube electrodes for stable [NiFe]-hydrogenase film voltammetry

We report on the use of polymyxin (PM), a cyclic cationic lipodecapeptide, as an electrode modifier for studying protein film voltammetry (PFV) on Au and single-walled carbon nanotube (SWNT) electrodes. Pretreating the electrodes with PM allows for the subsequent immobilization of an active submonolayer of [NiFe]-hydrogenase from Allochromatium vinosum ( Av H2ase). Probed by cyclic voltammetry (CV), the adsorbed enzyme exhibits characteristic electrocatalytic behavior that is stable for several hours under continuous potential cycling. An unexpected feature of the immobilization procedure is that the presence of chloride ions is a prerequisite for obtaining electrocatalytic activity. Atomic force microscopy (AFM) relates the observed catalytic activity to enzymatic adsorption at the PM/Au(111) surface, and a combination of concentration-dependent CV and AFM is used to investigate the interaction between the enzyme and the PM layer.     

Development of highly potent inhibitors of the ras-targeting human acyl protein thioesterases based on substrate similarity design

A matter of common sense: A common recognition motif consisting of a negatively charged group five to six bonds away (red) from the (thio)ester functionality (green) and a positively charged tail group ten to twelve bonds away (blue) was identified in two native acyl protein thioesterase?1 (APT1) substrates. This similarity led to the design of potent inhibitors of the Ras-depalmitoylating enzyme APT1.     

Complexation of divalent metal ions with diols in the presence of anion auxiliary ligands: zinc-induced oxidation of ethylene glycol to glycolaldehyde by consecutive hydride ion and proton shifts

Ternary complexes of the type AH???M(2+)???L(-) (AH?=?diol, including diethylene and triethylene glycol, M?=?Ca, Mn, Fe, Co, Ni, Cu and Zn and auxiliary anion ligand L(-) =?CH(3)COO(-), HCOO(-) and Cl(-)) have been generated in the gas phase by MALDI and ESI, and their dissociation characteristics have been obtained. Use of the auxiliary ligands enables the complexation of AH with the divalent metal ion without AH becoming deprotonated, although A(-)???M(2+) is often also generated in the ion source or after MS/MS. For M?=?Ca, dissociation occurs to AH?+?M(2+)???L(-) and/or to A(-)???M(2+) + LH, the latter being produced from the H-shifted isomer A(-) ???M(2+)???LH. For a given ligand L(-), the intensity ratio of these processes can be interpreted (barring reverse energy barriers) in terms of the quantity PA(A(-)) - Ca(aff) (A(-)), where PA is the proton affinity and Ca(aff) is the calcium ion affinity. Deuterium labeling shows that the complex ion HOCH(2)CH(2) OH???Zn(2+)???(-)OOCCH(3), in addition to losing acetic acid (60 Da), also eliminates glycolaldehyde (HOCH(2)CH=O, also 60 Da); it is proposed that these reactions commence with a hydride ion shift to produce the ion-dipole complex HOCH(2)CHOH(+)??? HZnOOCCH(3), which then undergoes proton transfer and dissociation to HOCH(2)CH=O?+?HZn(+)???O?=?C(OH)CH(3). In this reaction, ethylene glycol is oxidized by consecutive hydride ion and proton shifts. A minor process leads to loss of the isomeric species HOCH=CHOH.     

Path integrals for diffusion processes in Riemannian spaces

The Onsager-Machlup lagrangian for general continuous Markov processes in curved spaces will be derived invoking (i) continuous and differentiable trajectories, (ii) a Fourier series analysis of stochastic paths and (iii) the principle of general covariance. No discretization rule will be required in order to put the continuous action on a lattice.     

Light‐Controlled Histone Deacetylase (HDAC) Inhibitors: Towards Photopharmacological Chemotherapy

Cancer treatment suffers from limitations that have a major impact on the patient’s quality of life and survival. In the case of chemotherapy, the systemic distribution of cytotoxic drugs reduces their efficacy and causes severe side effects due to nonselective toxicity. Photopharmacology allows a novel approach to address these problems because it employs external, local activation of chemotherapeutic agents by using light. The development of photoswitchable histone deacetylase (HDAC) inhibitors as potential antitumor agents is reported herein. Analogues of the clinically used chemotherapeutic agents vorinostat, panobinostat, and belinostat were designed with a photoswitchable azobenzene moiety incorporated into their structure. The most promising compound exhibits high inhibitory potency in the thermodynamically less stable cis form and a significantly lower activity for the trans form, both in terms of HDAC activity and proliferation of HeLa cells. This approach offers a clear prospect towards local photoactivation of HDAC inhibition to avoid severe side effects in chemotherapy.     

Surface-charge-governed ion transport in nanofluidic channels

A study of ion transport in aqueous-filled silica channels as thin as 70 nm reveals a remarkable degree of conduction at low salt concentrations that departs strongly from bulk behavior: In the dilute limit, the electrical conductances of channels saturate at a value that is independent of both the salt concentration and the channel height. Our data are well described by an electrokinetic model parametrized only by the surface-charge density. Using chemical surface modifications, we further demonstrate that at low salt concentrations, ion transport in nanochannels is governed by the surface charge.     

Unstable state dynamics: A systematic evaluation of the master equation

The master equation for diffusion in a bistable potential is evaluated systematically in terms of the small-noise parameter for the case where the system is initially at the unstable state. The expansion is valid for all times, that is in the initial and intermediate as well as in the final regime. The theory does not involve free fitting parameters and is easily generalized to more complicated processes.     

A necessary condition forBSI-stability

This paper gives a negative result onBSI-stability for the Lobatto IIIC-methods with more than two stages. We also give a necessary condition forBSI-stability.