Evaluation of a Simplified Measurement for Low Glomerular Filtration Rates With lndium-111 DTPA

A rapid new method for measuring glomerular filtration rates using 111In diethylenetriamine pentaacetic acid (111In- DTPA) was evaluated with 39 patients who showed marked impairment of renal function (creatinine clearance less than 20 ml/min). A simple, single compartment system was assumed. For comparison, parallel inulin and creatinine clearances were performed. High linear correlations (r = 0.96-0.97) were demonstrated when 111In- DTPA clearances were compared with the standard nonisotopic tests. Initial data indicate that reliable isotopic clearance values could be obtained for low clearances by withdrawing only two blood samples for assay at 6 and 48 hours after isotope injection (without urine assay)

Kinetics of spontaneous filament nucleation via oligomers: Insights from theory and simulation

Nucleation processes are at the heart of a large number of phenomena, from cloud formation to protein crystallization. A recently emerging area where nucleation is highly relevant is the initiation of filamentous protein self-assembly, a process that has broad implications in many research areas ranging from medicine to nanotechnology. As such, spontaneous nucleation of protein fibrils has received much attention in recent years with many theoretical and experimental studies focussing on the underlying physical principles. In this paper we make a step forward in this direction and explore the early time behaviour of filamentous protein growth in the context of nucleation theory. We first provide an overview of the thermodynamics and kinetics of spontaneous nucleation of protein filaments in the presence of one relevant degree of freedom, namely the cluster size. In this case, we review how key kinetic observables, such as the reaction order of spontaneous nucleation, are directly related to the physical size of the critical nucleus. We then focus on the increasingly prominent case of filament nucleation that includes a conformational conversion of the nucleating building-block as an additional slow step in the nucleation process. Using computer simulations, we study the concentration dependence of the nucleation rate. We find that, under these circumstances, the reaction order of spontaneous nucleation with respect to the free monomer does no longer relate to the overall physical size of the nucleating aggregate but rather to the portion of the aggregate that actively participates in the conformational conversion. Our results thus provide a novel interpretation of the common kinetic descriptors of protein filament formation, including the reaction order of the nucleation step or the scaling exponent of lag times, and put into perspective current theoretical descriptions of protein aggregation.We acknowledge support from the Human Frontier Science Program and Emmanuel College (A.Š.), St John’s and Peterhouse Colleges (T.C.T.M.), the Swiss National Science Foundation (T.C.T.M.), the Biotechnology and Biological Sciences Research Council (T.P.J.K.), the Frances and Augustus Newman Foundation (T.P.J.K.), the European Research Council (T.C.T.M., T.P.J.K., and D.F.), and the Engineering and Physical Sciences Research Council (D.F.)

Plasmonic atoms and plasmonic molecules

The proposed paradigm of plasmonic atoms and plasmonic molecules allows one to describe and predict the strongly localized plasmonic oscillations in the clusters of nanoparticles and some other nanostructures in uniform way. Strongly localized plasmonic molecules near the contacting surfaces might become the fundamental elements (by analogy with Lego bricks) for a construction of fully integrated opto-electronic nanodevices of any complexity and scale of integration.Comment: 30 pages, 16 figure

Phase diagram of a generalized Winfree model

We study the phase diagram of a generalized Winfree model. The modification is such that the coupling depends on the fraction of synchronized oscillators, a situation which has been noted in some experiments on coupled Josephson junctions and mechanical systems. We let the global coupling k be a function of the Kuramoto order parameter r through an exponent z such that z=1 corresponds to the standard Winfree model, z<1 strengthens the coupling at low r (low amount of synchronization) and, at z>1, the coupling is weakened for low r. Using both analytical and numerical approaches, we find that z controls the size of the incoherent phase region, and one may make the incoherent behavior less typical by choosing z<1. We also find that the original Winfree model is a rather special case, indeed the partial locked behavior disappears for z>1. At fixed k and varying gamma, the stability boundary of the locked phase corresponds to a transition that is continuous for z1. This change in the nature of the transition is in accordance with a previous study on a similarly modified Kuramoto model.Comment: 9 pages, 3 figure

NBS monograph

From Introduction Statement of Objectives: "The purpose of this publication is to provide assistance to the practicing engineer who is faced with the problem of making dynamic measurements of rapidly changing pressures.

Kinetic constraints on self-assembly into closed supramolecular structures

Many biological and synthetic systems exploit self-assembly to generate highly intricate closed supramolecular architectures, ranging from self-assembling cages to viral capsids. The fundamental design principles that control the structural determinants of the resulting assemblies are increasingly well-understood, but much less is known about the kinetics of such assembly phenomena and it remains a key challenge to elucidate how these systems can be engineered to assemble in an efficient manner and avoid kinetic trapping. We show here that simple scaling laws emerge from a set of kinetic equations describing the self-assembly of identical building blocks into closed supramolecular structures and that this scaling behavior provides general rules that determine efficient assembly in these systems. Using this framework, we uncover the existence of a narrow range of parameter space that supports efficient self-assembly and reveal that nature capitalizes on this behavior to direct the reliable assembly of viral capsids on biologically relevant timescales