research. While good books on spatial point processes currently exist, this is the first to tackle difficult issues of simulation and simulation-based inference for such processes, including methods based on MCMC and related techniques. As the authors correctly note, as computer power and speed increase, and since analytic expressions for expectations of statistics for complex point process models are often unavailable, simulation-based approaches for spatial point processes should become increasingly important and widespread.Readers will find the text moderately difficult to read. It is about halfway between Brian Ripley's brilliantly simplistic "Spatial Statistics" and the far more theoretical "An Introduction to the Theory of Point Processes" by Daley and Vere-Jones, the latter of which deals little with spatial point processes but is widely (and correctly) considered the indispensable book on point processes in general. While Møller and Waagepetersen's book focuses on important practical topics such as simulation and inference, it is less a manual for applied statistics than a description of key concepts and mathematical results justifying important techniques used in applied research. Considering that the text states most results in their full mathematical precision and includes proofs of key theorems, it is remarkably easy to
Detergents are indispensable in the isolation of integral membrane proteins from biological membranes to study their intrinsic structural and functional properties. Solubilization involves a number of intermediary states that can be studied by a variety of physicochemical and kinetic methods; it usually starts by destabilization of the lipid component of the membranes, a process that is accompanied by a transition of detergent binding by the membrane from a noncooperative to a cooperative interaction already below the critical micellar concentration (CMC). This leads to the formation of membrane fragments of proteins and lipids with detergent-shielded edges. In the final stage of solubilization membrane proteins are present as protomers, with the membrane inserted sectors covered by detergent. We consider in detail the nature of this interaction and conclude that in general binding as a monolayer ring, rather than as a micelle, is the most probable mechanism. This mode of interaction is supported by neutron diffraction investigations on the disposition of detergent in 3-D crystals of membrane proteins. Finally, we briefly discuss the use of techniques such as analytical ultracentrifugation, size exclusion chromatography, and mass spectrometry relevant for the structural investigation of detergent solubilized membrane proteins.
We view the locations and times of a collection of crime events as a space-time point pattern. So, with either a nonhomogeneous Pois-son process or with a more general Cox process, we need to specify a space-time intensity. For the latter, we need a random intensity which we model as a realization of a spatio-temporal log Gaussian process. Importantly, we view time as circular not linear, necessitating valid separable and nonseparable covariance functions over a bounded spatial region crossed with circular time. In addition, crimes are classified by crime type. Furthermore, each crime event is recorded by day of the year which we convert to day of the week marks. The contribution here is to develop models to accommodate such data. Our specifications take the form of hierarchical models which we fit within a Bayesian framework. In this regard, we consider model comparison between the nonhomogeneous Poisson process and the log Gaussian Cox process. We also compare separable vs. nonseparable covariance specifications. Our motivating dataset is a collection of crime events for the city of San Francisco during the year 2012. We have location, hour, day of the year, and crime type for each event. We investigate models to enhance our understanding of the set of incidences.
A tight coupling between adenosine triphosphate (ATP) hydrolysis and vectorial ion transport has to be maintained by ATP-consuming ion pumps. We report two crystal structures of Ca2+-bound sarco(endo)plasmic reticulum Ca2+-adenosine triphosphatase (SERCA) at 2.6 and 2.9 angstrom resolution in complex with (i) a nonhydrolyzable ATP analog [adenosine (beta-gamma methylene)-triphosphate] and (ii) adenosine diphosphate plus aluminum fluoride. SERCA reacts with ATP by an associative mechanism mediated by two Mg2+ ions to form an aspartyl-phosphorylated intermediate state (Ca2-E1 approximately P). The conformational changes that accompany the reaction with ATP pull the transmembrane helices 1 and 2 and close a cytosolic entrance for Ca2+, thereby preventing backflow before Ca2+ is released on the other side of the membrane.
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