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The role of orthophosphate ions (Pi) in crossbridge kinetics was investigated by parallel measurements of the ATP hydrolysis rate and tension transients in maximally activated, chemically skinned rabbit psoas fibers. The hydrolysis rate of the standard activation at 20 degrees C was measured at 1.25 nmole X s-1 X m-1 X fiber-1, which corresponds to the hydrolysis of 3 moles ATP per mole of myosin head per second. The isometric tension, stiffness extrapolated to the infinite frequency, and the ATPase rate progressively decreased when increasing concentrations of Pi (0-16 mM) were added to the activating saline. The decrease was greatest with tension, followed by stiffness and the ATPase rate. Both the apparent rate constant and the magnitude parameters of exponential process (B) increased with Pi concentration resulting in a significant increase in the oscillatory power output. The effects of Pi on processes (A) and (C) were only marginal. When fibers were oscillated at 1 Hz [close to the characteristic frequency of process (A)], no significant increase in the ATP hydrolysis rate was observed. However, a small increase was noticed at 10 Hz [1%, process (B)], and at 100 Hz [6%, process (C)]. We interpret these results in terms of a crossbridge scheme which adds a branch pathway to the conventional hydrolysis cycle. In the proposed scheme, the number of crossbridges entering the branch pathway increases at higher Pi concentrations and in the presence of imposed oscillations at the proper frequency.

A comprehensive nanoscale understanding of layered double hydroxide (LDH) thermal evolution is critical for their current and future applications as catalysts, flame retardants and oxygen evolution performers. In this report, we applied in situ transmission electron microscopy (TEM) to extensively characterise the thermal progressions of nickel-iron containing (Ni-Fe) LDH nanomaterials. The combinative approach of TEM and selected area electron diffraction (SAED) yielded both a morphological and crystallographic understanding of such processes. As the Ni-Fe LDH nanomaterials are heated in situ, an amorphization occurred at 250°C, followed by a transition to a heterogeneous structure of NiO particles embedded throughout a NiFe 2 O 4 matrix at 850°C, confirmed by highresolution TEM and scanning TEM. Further electron microscopy characterisation methodologies of energy-filtered TEM were utilised to directly observe these mechanistic behaviours in real time, showing an evolution and nucleation to an array of spherical NiO nanoparticles on the platelet surfaces. The versatility of this characterisation approach was verified by the analogous behaviours of Ni-Fe LDH materials heated ex situ as well as parallel in situ TEM and SAED comparisons to that of an akin magnesium-aluminium containing (Mg-Al) LDH structure. The in situ TEM work hereby discussed allows for a state-of-the-art understanding of the Ni-Fe material thermal evolution. This is an important first, which reveals pivotal information, especially when considering LDH applications as catalysts and flame retardants.

A micro cuvette is described, which allows to measure mechanical, optical and energetic parameters of single skinned muscle fibres or small fibre bundles. Two examples for possible applications are given: The measurement of ATPase activity of single muscle fibres. The detection of fluorescence changes due to Ca binding to fluorescence labeled TnC, which was incorporated into small bundles of rabbit psoas fibres before the experiment.

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