The structural and magnetic properties of room-temperature ͑RT: 300 K͒-grown and low-temperature ͑LT: 100 K͒-grown Mn/ Cu 3 Au͑100͒ thin films were investigated. Mn films deposited at RT and LT demonstrate very different behaviors in the crystalline structure, morphology, and magnetism. RT-Mn films reveal apparent layer-by-layer growth for 0 -2 ML ͑monolayer͒ followed by reduced oscillations. Although the medium-energy electron diffraction ͑MEED͒ oscillation is reduced, the intensity of specular spot increases monotonically after 6 -7 ML, inferring the tendency of smooth morphology. The study of scanning tunneling microscopy also shows that even in 19 ML Mn/ Cu 3 Au͑100͒, the surface morphology is composed of large terraces with the size up to hundreds of nanometers. The LT-Mn films reveal apparent layer-by-layer growth for 0 -5 ML followed by the reduced oscillations, and then the MEED intensity remains at low intensity, inferring the rough surface. The RT-and LT-Mn films exhibit a thickness-dependent structural transition from a face-centered cubic to a face-centered tetragonal structure at different critical thicknesses, ϳ12-14 and ϳ8 ML, respectively. Significant exchange bias is observed in Fe/ RT-Mn bilayers. It increases monotonously with Mn thickness. The exchange bias coupling in Fe/ LT-Mn is much weaker than Fe/ RT-Mn and drastically varies with Mn film thickness. The presence of exchange bias in the Fe/ Mn bilayers also indicates the antiferromagnetism of ␥-phase Mn/ Cu 3 Au͑100͒.

The voltage-sensing domains of voltage-gated potassium channels Kv2.1 (drk1) contain four transmembrane segments in each subunit, termed S1 to S4. While S4 is known as the voltage sensor, the carboxyl terminus of S3 (S3C) bears a gradually broader interest concerning the site for gating modifier toxins like hanatoxin and thus the secondary structure arrangement as well as its surrounding environment. To further examine the putative three-dimensional (3-D) structure of S3C and to illustrate the residues required for hanatoxin binding (which may, in turn, show the influence on the S4 in terms of changes in channel gating), molecular simulations and dockings were performed. These were based on the solution structure of hanatoxin and the structural information from lysine-scanning results for S3C fragment. Our data suggest that several basic and acidic residues of hanatoxin are electrostatically and stereochemically mapped onto their partner residues on S3C helix, whereas some aromatic or hydrophobic residues located on the same helical fragment interact with the hydrophobic patch of the toxin upon binding. Therefore, a slight distortion of the S3C helix, in a direction toward the N-terminus of S4, may exist. Such conformational change of S3C upon toxin binding is presented as a possible explanation for the observed shift in hanatoxin binding-induced gating.

The voltage-sensing domains of voltage-gated potassium channels Kv2.1 (drk1) contain four transmembrane segments in each subunit, termed S1 to S4. While S4 is known as the voltage sensor, the carboxyl terminus of S3 (S3C) bears a gradually broader interest concerning the site for gating modifier toxins like hanatoxin and thus the secondary structure arrangement as well as its surrounding environment. To further examine the putative three-dimensional (3-D) structure of S3C and to illustrate the residues required for hanatoxin binding (which may, in turn, show the influence on the S4 in terms of changes in channel gating), molecular simulations and dockings were performed. These were based on the solution structure of hanatoxin and the structural information from lysine-scanning results for S3C fragment. Our data suggest that several basic and acidic residues of hanatoxin are electrostatically and stereochemically mapped onto their partner residues on S3C helix, whereas some aromatic or hydrophobic residues located on the same helical fragment interact with the hydrophobic patch of the toxin upon binding. Therefore, a slight distortion of the S3C helix, in a direction toward the N-terminus of S4, may exist. Such conformational change of S3C upon toxin binding is presented as a possible explanation for the observed shift in hanatoxin binding-induced gating.

Ultrathin γ-phase (face-center cubic) Mn films were prepared by epitaxial growth on Cu3Au(100). Kinematic analysis of low energy electron diffraction I∕V showed a structure transformation of Mn films from nearly face-center cubic to face-center tetragonal with increasing coverage. No ferromagnetic signal in Mn∕Cu3Au(100) was observed. For 21 ML capping film of Fe on Mn films, the hysteresis loop of Fe was biased. The bias field for 21MLFe∕15MLMn∕Cu3Au(100) was ∼200Oe at 110 K with the blocking temperature Tb∼300K. This observation of exchange bias substantiates the theoretical prediction of antiferromagnetism in γ-phase Mn.