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It is shown that microwave irradiation can affect the kinetics of the folding process of some globular proteins, especially ␤-lactoglobulin. At low temperature the folding from the cold denatured phase of the protein is enhanced, while at a higher temperature the denaturation of the protein from its folded state is enhanced. In the latter case, a negative temperature gradient is needed for the denaturation process, suggesting that the effects of the microwaves are nonthermal. This supports the notion that coherent topological excitations can exist in proteins. The application of microwaves hold promises for a wide range of biotechnological applications, such as protein synthesis, protein aggregation, etc., and may have implications for biological systems as well.

We present experimental and numerical results demonstrating the drastic influence of attractive forces on the behaviour of the atomic force microscope when operated in the resonant tapping tip mode in an ambient environment. It is often assumed that tapping is related to repulsive interaction. In contrast, we find that in general the attractive forces are the most dominant interaction in this mode of operation. We show that attractive forces in combination with the repulsive elastic type of forces cause points of instability in the parameter space constituted by: the cantilever swing amplitude, the frequency bias point, and the distance between the fixed end of the cantilever and the sample. These points of instability can result in disturbances during image acquisition on hard elastic surfaces.

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We present the results of magnetic x-ray scattering experiments on the rare-earth metal holmium using synchrotron radiation. Direct high-resolution measurements of the nominally incommensurate magnetic satellite reflections reveal new lock-in behavior which we explain within a simple spin-discommensuration model. As a result of magnetoelastic coupling, the spin-discommensuration array produces additional x-ray diffraction satellites. Their observation further substantiates the model and demonstrates additional advantages of synchrotron radiation for magnetic-structure studies.PACS numbers: 61.10. Fr, An x-ray incident on an electron is scattered by both the electron's charge and its magnetic moment. Charge scattering is the dominant mechanism and is the basis for structural investigations of condensed matter by x-ray diffraction. In the first application of magnetic x-ray scattering, de Bergevin and Brunei 1,2 performed experiments on the antiferromagnet NiO using a fixed-target x-ray tube. Subsequently, there have been experimental 3 and theoretical 4 developments, but progress to date has been limited by the fact that the magnetic x-ray scattering cross section is substantially smaller than the Thomson cross section for charge scattering. Even in the most favorable cases, 3,4 the ratio of magnetic to charge scattering is less than = 10" 5 . As we will show, however, easily measured signals are obtained with the intense synchrotron radiation beams available from wiggler sources.In this paper we present high-resolution magnetic x-ray scattering studies of the incommensurate magnetic spiral in the rare-earth metal holmium. During the last decade, investigations of various incommensurate systems, such as charge-density wave materials 5 and graphite intercalates, 6 have revealed microscopically inhomogeneous structures composed of commensurate regions separated by localized regions of large incommensurability called discommensurations. 7 The high resolution naturally provided with synchrotron x-ray scattering methods 8 permits direct study of structural correlations on the long spatial length scales inherent in these systems. High resolution is also crucial in the present experiments, which have led to a new model 9 of the magnetic structure of rare earths based on the concept of spin discommensurations. Results from both x-ray and complementary neutron scattering experiments on the same sample are reported.For the synchrotron experiments carried out at the Stanford Synchrotron Radiation Laboratory, a Ho single crystal (7x3x1 mm 3 ) grown by R. J. Gambino at IBM was mounted in a variable-temperature cryostat and studied in reflection. The initial experiments were performed on the Exxon/LBL/SSRL 54-pole wiggler beam line VI-2 with X= 1.7 A; further measurements involving polarization analysis were performed on the 8-pole wiggler beam line VII-2 with \= 1.5 A. In each experiment a Si or Ge double-crystal monochromator was used with a Ge analyzer in the standard vertical diffraction geometry. The illuminated sample are...

To produce biominerals, such as shells, bones, and teeth, living beings create organic compounds that control the growth of the solid phase. Investigating the atomic scale behavior of individual functional groups at the mineral-fluid interface provides fundamental information that is useful for constructing accurate predictive models for natural systems. Previous investigations of the activity of coccolith-associated polysaccharides (CAP) on calcite, using atomic force microscopy (AFM) [Henriksen, K., Young, J. R., Bown, P. R., and Stipp, S. L. S. Palentology 2004, 43 (Part 3), 725-743] and molecular dynamics (MD) modeling [Yang, M., Stipp, S. L. S., and Harding, J. H. Cryst. Growth Des. 2008, 8 (11), 4066-4074], have suggested that OH functional groups control polysaccharide attachment. The purpose of this work was to characterize, using X-ray reflectivity (XR) combined with molecular dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH(3)-CH(2)-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol molecules stand up perpendicularly at the interface or nearly so. As a consequence, the fatty, CH(3) ends form a new surface, about 6 Å from the termination of the bulk calcite, and beyond that, there is a thin gap where ethanol density is low. Following is a more disordered layer that is two to three ethanol molecules thick, about 14 Å, where density more resembles that of bulk liquid ethanol. The good agreement between theory and experiment gives confidence that a theoretical approach can offer information about behavior in more complex systems.