Membrane redox as an essential component of how cells increase in size following cell division

Under investigation is the hypothesis that cell enlargement in both plants and animals is not a passive process but the result of an ECTO-NOX-driven physical membrane displacement. Cell enlargement correlates with ECTO-NOX activity and is stimulated when ECTO-NOX activities are stimulated and inhibited when ECTO-NOX activities are inhibited. Both are blocked by thiol reagents. Additionally, cell enlargement emerges as having an energy requirement. An energy requirement is universal among membrane displacement models and is met at the cell surface through coupling with a plasma membrane-associated AAA-ATPase

Role of membrane redox in aging-related diseases

A number of different ECTO-NOX forms have been described as being connected with aging-related diseases. The constitutive form, CNOX, serves as a terminal oxidase of plasma membrane electron transport and functions in the growth process. tNOX is present in addition to CNOX on the surface of all cancer cells and contributes to the unregulated growth characteristic of cancer cells. An age-related ECTO-NOX, arNOX, generates superoxide and may contribute to age-related generation of reactive oxygen species. ECTO-NOX proteins and prions share properties in common as do amyloid-forming proteins of various neurodegenerative disorders. A better understanding of ECTO-NOX proteins may lead to new therapeutic strategies for these several age-related disorders

STRUCTURAL CHANGES REVEALED BY FOURIER TRANSFORM INFRARED AND CIRCULAR DICHROISM SPECTROSCOPIC ANALYSES UNDERLIE tNOX PERIODIC OSCILLATIONS

A recurring pattern of spectral changes indicative of periodic changes in the proportion of β-structure and α-helix of a recombinant ECTO-NOX fusion protein of tNOX, with a cellulose binding domain peptide, was demonstrated by Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopic analyses. The pattern of structural changes correlated with oscillatory patterns of enzymatic activities exhibited by the protein previously interpreted as indicative of a clock function. The pattern consisted of a repeating pattern of oscillations with a period length of 21 min with five maxima (two separated by 5 min and 3 separated by 4 to 4.5 min) within each 21 min repeat. Oscillatory patterns were not obvious in comparable FTIR or CD spectra of albumin, ribonuclease or concanavalin A. The period length was constant at 5, 15, 25, 35 and 45° C (temperature compensated) and oscillations occurred independently of substrate presence. Spectra obtained in deuterium oxide yielded a longer period length of 26 min both for oscillations in enzymatic activity and absorbance ratios determined by FTIR. Taken together the findings suggest that the regular patterns of oscillations exhibited by the ECTO-NOX proteins are accompanied by recurrent global changes in the conformation of the protein backbone that directly modulate enzymatic activity

First order phase transition of the vortex lattice in twinned YBa2Cu3O7 single crystals in tilted magnetic fields

We present an exhaustive analysis of transport measurements performed in twinned YBa2Cu3O7 single crystals which stablishes that the vortex solid-liquid transition is first order when the magnetic field H is applied at an angle theta away from the direction of the twin planes. We show that the resistive transitions are hysteretic and the V-I curves are non-linear, displaying a characteristic s-shape at the melting line Hm(T), which scales as epsilon(theta)Hm(T,theta). These features are gradually lost when the critical point H*(theta) is approached. Above H*(theta) the V-I characteristics show a linear response in the experimentally accessible V-I window, and the transition becomes reversible. Finally we show that the first order phase transition takes place between a highly correlated vortex liquid in the field direction and a solid state of unknown symmetry. As a consequence, the available data support the scenario for a vortex-line melting rather than a vortex sublimation as recently suggested [T.Sasagawa et al. PRL 80, 4297 (1998)].Comment: 10 pages, 8 figures, submitted to PR