Active Membrane Fluctuations Studied by Micropipet Aspiration

We present a detailed analysis of the micropipet experiments recently reported in J-B. Manneville et al., Phys. Rev. Lett. 82, 4356--4359 (1999), including a derivation of the expected behaviour of the membrane tension as a function of the areal strain in the case of an active membrane, i.e., containing a nonequilibrium noise source. We give a general expression, which takes into account the effect of active centers both directly on the membrane, and on the embedding fluid dynamics, keeping track of the coupling between the density of active centers and the membrane curvature. The data of the micropipet experiments are well reproduced by the new expressions. In particular, we show that a natural choice of the parameters quantifying the strength of the active noise explains both the large amplitude of the observed effects and its remarkable insensitivity to the active-center density in the investigated range. [Submitted to Phys Rev E, 22 March 2001]Comment: 14 pages, 5 encapsulated Postscript figure

Commemorating conquest: The triumphal entry of William III of Orange, King of England, into The Hague in 1691

Contemporary sources described the triumphal entry of William III as the most magnificent spectacle of the so-called Dutch Golden Age. Triumphal arches and firework displays were built to mark William’s first return to the Republic since the Glorious Revolution while numerous foreign princes and diplomats travelled from far to meet the new King of England. Seventeenth-century observers focused on William’s representation in the triumphal entry, its temporary architecture and the medals struck to commemorate this occasion, rather than subsequent depiction of these events in prints, which has been the focus of modern scholarship. This thesis defines the triumphal entry as a form of ritual involving people and objects in order to analyze the relation between the event and its cultural and political significance. It argues that its design, purpose and impact can only be understood in the context of the Glorious Revolution and William’s constant struggle against Louis XIV of France. As a successor state, the Anglo-Dutch monarchy required the fabrication of new traditions to sustain an appearance of legitimacy and negotiate the break with the past. But the claims of the triumphal entry were ambiguous and reactions across Europe ranged from exuberant praise to accusations of tyranny and usurpation. French critics pointed out that William’s portrayal as a Roman conqueror revealed the true nature of his ambitions and contradicted the conciliatory promises of his post-revolutionary reign.  Collective identities and transnational networks in medieval and early modern Europe, 1000-180

‘Les meilleures architectes du roi’. Een onbekende brief uit 1628 over de vroege bouwperiode van het Huis Honselaarsdijk

This article examines a recently discovered letter written to Stadtholder Frederik Hendrik of Orange by his French agent Nicolas Tassin in 1628 concerning the improvement of the palace and gardens of Honselaarsdijk in the Netherlands. Although Frederik Hendrik had already started renovating his estate in 1621 there is very little information about the period between 1621 and 1633. The 1628 letter is therefore a rare and valuable source for the early phase of Honselaarsdijk’s history. With his letter, Tassin enclosed a ground plan for a redesign of Honselaarsdijk made according to the advice of the ‘best architects of the king’ [of France]. This confirms the hypothesis that French architects were involved in the design of Honselaarsdijk from an early stage. Although the 1628 ground plan did not survive, Tassin’s description of the plan suggested changes to the building, which were duly carried out by Pieter Post from 1646 onwards (figs. 4, 5, 8). Unfortunately, the letter does not mention the names of the ‘best architects of the king’ Tassin had consulted in France. It is, however, most likely that one of those French architects was Jacques Lemercier. Lemercier can be linked to two other Frenchmen who later worked for Frederik Hendrik: the master mason and architect Simon de la Vallée and the gardener André Mollet, who worked at the same time on one of Lemercier’s court commissions. De la Vallée and André Mollet both started to work for Frederik Hendrik in 1633.The 1628 letter reveals another interesting connection between France and the court of the stadtholder: Tassin had approached Jacques Boyceau de la Baraudière to design parterres for the gardens at Honselaarsdijk. This confirms the hypothesis that the celebrated gardener contributed to Honselaarsdijk’s gardens before the arrival of Claude Mollet in 1633. Although further details are lacking (such as Frederik Hendrik’s response and both previous and subsequent correspondence on these matters), the letter is an important early record of Frederik Hendrik’s royal ambitions as architectural patron

‘Les meilleures architectes du roi’. Een onbekende brief uit 1628 over de vroege bouwperiode van het Huis Honselaarsdijk

This article examines a recently discovered letter written to Stadtholder Frederik Hendrik of Orange by his French agent Nicolas Tassin in 1628 concerning the improvement of the palace and gardens of Honselaarsdijk in the Netherlands. Although Frederik Hendrik had already started renovating his estate in 1621 there is very little information about the period between 1621 and 1633. The 1628 letter is therefore a rare and valuable source for the early phase of Honselaarsdijk’s history. With his letter, Tassin enclosed a ground plan for a redesign of Honselaarsdijk made according to the advice of the ‘best architects of the king’ [of France]. This confirms the hypothesis that French architects were involved in the design of Honselaarsdijk from an early stage. Although the 1628 ground plan did not survive, Tassin’s description of the plan suggested changes to the building, which were duly carried out by Pieter Post from 1646 onwards (figs. 4, 5, 8). Unfortunately, the letter does not mention the names of the ‘best architects of the king’ Tassin had consulted in France. It is, however, most likely that one of those French architects was Jacques Lemercier. Lemercier can be linked to two other Frenchmen who later worked for Frederik Hendrik: the master mason and architect Simon de la Vallée and the gardener André Mollet, who worked at the same time on one of Lemercier’s court commissions. De la Vallée and André Mollet both started to work for Frederik Hendrik in 1633.The 1628 letter reveals another interesting connection between France and the court of the stadtholder: Tassin had approached Jacques Boyceau de la Baraudière to design parterres for the gardens at Honselaarsdijk. This confirms the hypothesis that the celebrated gardener contributed to Honselaarsdijk’s gardens before the arrival of Claude Mollet in 1633. Although further details are lacking (such as Frederik Hendrik’s response and both previous and subsequent correspondence on these matters), the letter is an important early record of Frederik Hendrik’s royal ambitions as architectural patron

Proteomic profiling of mitochondria: what does it tell us about the ageing brain?

Mitochondrial dysfunction is evident in numerous neurodegenerative and age-related disorders. It has also been linked to cellular ageing, however our current understanding of the mitochondrial changes that occur are unclear. Functional studies have made some progress reporting reduced respiration, dynamic structural modifications and loss of membrane potential, though there are conflicts within these findings. Proteomic analyses, together with functional studies, are required in order to profile the mitochondrial changes that occur with age and can contribute to unravelling the complexity of the ageing phenotype. The emergence of improved protein separation techniques, combined with mass spectrometry analyses has allowed the identification of age and cell-type specific mitochondrial changes in energy metabolism, antioxidants, fusion and fission machinery, chaperones, membrane proteins and biosynthesis pathways. Here, we identify and review recent data from the analyses of mitochondria from rodent brains. It is expected that knowledge gained from understanding age-related mitochondrial changes of the brain should lead to improved biomarkers of normal ageing and also age-related disease progression

Proteomic DIGE analysis of the mitochondria-enriched fraction from aged rat skeletal muscle

Skeletal muscle aging is associated with a loss in tissue mass and contractile strength, as well as fiber type shifting and bioenergetic adaptation processes. Since mitochondria represent the primary site for energy generation via oxidative phosphorylation, we investigated potential changes in the expression pattern of the mitochondrial proteome using the highly sensitive DIGE approach. The comparative analysis of the mitochondria-enriched fraction from young adult versus aged muscle revealed an age-related change in abundance for 39 protein species. MS technology identified the majority of altered proteins as constituents of muscle mitochondria. An age-dependent increase was observed for NADH dehydrogenase, the mitochondrial inner membrane protein mitofilin, peroxiredoxin isoform PRX-III, ATPase synthase, succinate dehydrogenase, mitochondrial fission protein Fis1, succinate-coenzyme A ligase, acyl-coenzyme A dehydrogenase, porin isoform VDAC2, ubiquinol-cytochrome c reductase core I protein and prohibitin. Immunoblotting, enzyme testing and confocal microscopy were used to validate proteomic findings. The DIGE-identified increase in key mitochondrial elements during aging agrees with the concept that sarcopenia is associated with a shift to a slower contractile phenotype and more pronounced aerobic-oxidative metabolism. This suggests that mitochondrial markers are reliable candidates that should be included in the future establishment of a biomarker signature of skeletal muscle aging

Role of Mitochondrial Protein Import in Age-Related Neurodegenerative and Cardiovascular Diseases

Mitochondria play a critical role in providing energy, maintaining cellular metabolism, and regulating cell survival and death. To carry out these crucial functions, mitochondria employ more than 1500 proteins, distributed between two membranes and two aqueous compartments. An extensive network of dedicated proteins is engaged in importing and sorting these nuclear-encoded proteins into their designated mitochondrial compartments. Defects in this fundamental system are related to a variety of pathologies, particularly engaging the most energy-demanding tissues. In this review, we summarize the state-of-the-art knowledge about the mitochondrial protein import machinery and describe the known interrelation of its failure with age-related neurodegenerative and cardiovascular diseases

Dynamics of hydration water in deuterated purple membranes explored by neutron scattering

The function and dynamics of proteins depend on their direct environment, and much evidence has pointed to a strong coupling between water and protein motions. Recently however, neutron scattering measurements on deuterated and natural-abundance purple membrane (PM), hydrated in H2O and D2O, respectively, revealed that membrane and water motions on the ns–ps time scale are not directly coupled below 260 K (Wood et al. in Proc Natl Acad Sci USA 104:18049–18054, 2007). In the initial study, samples with a high level of hydration were measured. Here, we have measured the dynamics of PM and water separately, at a low-hydration level corresponding to the first layer of hydration water only. As in the case of the higher hydration samples previously studied, the dynamics of PM and water display different temperature dependencies, with a transition in the hydration water at 200 K not triggering a transition in the membrane at the same temperature. Furthermore, neutron diffraction experiments were carried out to monitor the lamellar spacing of a flash-cooled deuterated PM stack hydrated in H2O as a function of temperature. At 200 K, a sudden decrease in lamellar spacing indicated the onset of long-range translational water diffusion in the second hydration layer as has already been observed on flash-cooled natural-abundance PM stacks hydrated in D2O (Weik et al. in J Mol Biol 275:632–634, 2005), excluding thus a notable isotope effect. Our results reinforce the notion that membrane-protein dynamics may be less strongly coupled to hydration water motions than the dynamics of soluble proteins