The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure

Aminopyrazine Inhibitors Binding to an Unusual Inactive Conformation of the Mitotic Kinase Nek2: SAR and Structural Characterization

We report herein the first systematic exploration of inhibitors of the mitotic kinase Nek2. Starting from HTS hit aminopyrazine 2, compounds with improved activity were identified using structure-based design. Our structural biology investigations reveal two notable observations. First, 2 and related compounds bind to an unusual, inactive conformation of the kinase which to the best of our knowledge has not been reported for other types of kinase inhibitors. Second, a phenylalanine residue at the center of the ATP pocket strongly affects the ability of the inhibitor to bind to the protein. The implications of these observations are discussed, and the work described here defines key features for potent and selective Nek2 inhibition, which will aid the identification of more advanced inhibitors of Nek2

Signals in abscission.

Abscission is the term used to describe the process of natural separation of organs from the parent plant. This may be part of the highly programmed development of a plant, or in response to environmental stress. It enables temperate plants to overwinter and hence survive, but in agricultural or horticultural environments premature abscission can lead to significant crop losses. Abscission is the culmination of changes in gene expression, which result in the loosening of adjacent cell walls within the zone and subsequent cell separation. For many years it has been recognized that the balance between the plant hormones ethylene and auxin determine where, and when, separation takes place. As we begin to understand the mechanisms by which plant growth regulator signals are perceived and transduced, we can begin to understand how the process of abscission itself may be induced and regulated. This review details what we know of the signals that lead to the differentiation of zone cells; the environmental signals that promote cell separation, and the possible intracellular signalling events that culminate in organ shedding

The pivotal role of the β7 strand in the intersubunit contacts of different human small heat shock proteins

Human αB-crystallin and small heat shock proteins HspB6 and HspB8 were mutated so that all endogenous Cys residues were replaced by Ser and the single Cys residue was inserted in a position homologous to that of Cys137 of human HspB1, i.e. in a position presumably located in the central part of β7 strand of the α-crystallin domain. The secondary, tertiary, and quaternary structures of thus obtained Cys-mutants as well as their chaperone-like activity were similar to those of their wild-type counterparts. Mild oxidation of Cys-mutants leads to formation of disulfide bond crosslinking neighboring monomers thus indicating participation of the β7 strand in intersubunit interaction. Oxidation weakly affects the secondary and tertiary structure, does not affect the quaternary structure of αB-crystallin and HspB6, and shifts equilibrium between monomer and dimer of HspB8 towards dimer formation. It is concluded that the β7 strand participates in the intersubunit interaction of four human small heat shock proteins (αB-crystallin, HspB1, HspB6, HspB8) having different structure of β2 strand of α-crystallin domain and different length and composition of variable N- and C-terminal tails