Communication: Resonance reaction in diffusion-influenced bimolecular reactions

We investigate the influence of a stochastically fluctuating step-barrier potential on bimolecular reaction rates by exact analytical theory and stochastic simulations. We demonstrate that the system exhibits a new "resonant reaction" behavior with rate enhancement if an appropriately defined fluctuation decay length is of the order of the system size. Importantly, we find that in the proximity of resonance, the standard reciprocal additivity law for diffusion and surface reaction rates is violated due to the dynamical coupling of multiple kinetic processes. Together, these findings may have important repercussions on the correct interpretation of various kinetic reaction problems in complex systems, as, e.g., in biomolecular association or catalysis

The Feminisation U, cultural norms, and the plough

The Feminisation U describes the tendency of female labour force participation (FLFP) to first decline and then rise in the process of economic development. While the Feminisation U is often presented as a ‘stylised fact’ of development, empirical support for it is mixed. Here, we show that cultural norms inherited from ancestral plough use exert a moderating influence on the shape of the Feminisation U. Specifically, we find a significantly U-shaped path of FLFP only in countries whose ancestors employed a plough-based agricultural technology. The shape of the U-curve becomes progressively more muted as the share of a country's ancestors that practiced plough agriculture decreases. In countries with little or no legacy of historical plough use, the time path of FLFP is effectively flat. This pattern of results is robust to correcting for dynamic panel bias, instrumenting for per-capita income, and controlling for other potential effect modifiers. Our findings are compatible with a nuanced reading of the main theoretical models proposed in the literature to explain the Feminisation U

Competitive adsorption of multiple proteins to nanoparticles: the Vroman effect revisited

Proteins adsorbed from the blood plasma change nanoparticles inter- actions with the surrounding biological environment. In general, the ad- sorption of multiple proteins has a non-monotonic time dependence, that is, proteins adsorbed at first may slowly be replaced by others. This “Vro- man effect” leads to a highly dynamic protein corona on nanoparticles that profoundly influences the immune response of the body. Thus, the temporal evolution of the corona must be taken into account when consid- ering applications of nanocarriers in, e.g., nanomedicine or drug delivery. Up to now, the Vroman effect is explained solely in terms of diffusion: Smaller proteins which diffuse faster are adsorbed first while larger ones, having a stronger interaction with the surface, are preferred at equilib- rium. Here we use dynamic density functional theory (DDFT) including steric and electrostatic interactions to provide a full model for the tem- poral evolution of the protein corona. In particular, we demonstrate that proper consideration of all interactions leads to Vroman-like adsorption signatures in widely different scenarios. Moreover, consideration of ener- getic terms predicts both competitive as well as co-operative adsorption. In this way, DDFT provides a reacher picture of the evolution of the dynamic protein coron

A general theory of DNA-mediated and other valence-limited interactions

We present a general theory for predicting the interaction potentials between DNA-coated colloids, and more broadly, any particles that interact via valence-limited ligand-receptor binding. Our theory correctly incorporates the configurational and combinatorial entropic factors that play a key role in valence-limited interactions. By rigorously enforcing self-consistency, it achieves near-quantitative accuracy with respect to detailed Monte Carlo calculations. With suitable approximations and in particular geometries, our theory reduces to previous successful treatments, which are now united in a common and extensible framework. We expect our tools to be useful to other researchers investigating ligand-mediated interactions. A complete and well-documented Python implementation is freely available at http://github.com/patvarilly/DNACC .Comment: 18 pages, 10 figure

Unfolded P53 as a novel lead biomarker for Alzheimer's disease diagnosis

AbstractBackgroundBlood‐based biomarkers represent a promising choice for early Alzheimer's disease (AD) diagnosis and for evaluating the efficacy of novel disease‐modifying therapeutics.The complexity of the disease, where multiple pathogenetic mechanisms are involved, would require a pragmatic approach that includes a biomarkers panel for an individually‐tailored AD diagnosis. Oxidative stress, reactive oxygen and nitrogen species have been well documented in AD, however the potential use in the clinic of the metalloprotein p53 as a lead biomarker for this devastating neurodegenerative disorder has not yet been thoroughly investigated. Thus, the aim of this study was to evaluate the role of a conformational variant of p53 as a lead biomarker (Up532D3A8+) in plasma samples from AD at the pre‐clinical and prodromal stages.MethodPlasma samples from Australian Imaging, Biomarkers and Lifestyle cohort (AIBL) biobank were used to evaluate the concentration of Up532D3A8+ through immunoprecipitation with the 2D3A8 antibody followed by SRM‐MS. A total of 102 plasma samples was studied, which includes at baseline samples from (a) AD patients, (b) Mild Cognitive Impairments (MCI) patients and (c) cognitive normal (CN) individuals, in addition to samples at a later time‐point from (d) individuals that converted to AD in a period of 18‐72 months, (e) MCI patients that converted to AD in a period of 18‐36 months and (f) MCI patients at baseline that have not declined to AD for a period of 36 months. Through using a standard heavy isotype labelled peptide spiked into clinical sample before the assay such as plasma, the absolute abundance of Up532D3A8+ protein isoform or its partial degradation products was measured accurately with a high sensitivity.ResultA specific peptide of Up532D3A8+ as signature of clinical AD progression was detected by 2D3A8 immunoprecipitation and quantified by SRM‐MS. This peptide showed a prognostic value with a sensitivity >90%, specificity >85%, PPV around 80%, NPV >95%.ConclusionThe study presented here strongly supports Up532D3A8+ as a promising lead AD biomarker, in particular for disease prognosis in its asymptomatic stage. Consequently it may become an indispensable tool for patient stratification for clinical trials that aim for the prevention of dementia stage in AD progression

Modeling Au nanostar geometry in bulk solutions.

The findings within make it possible to reference gold nanostars based on their geometric properties, similar to how a radius describes a nanosphere, rather than just the LSPR of the structure-the current practice. The average tip approximation presented reduces the complexity of nanostars in discrete dipole approximation simulations. By matching the projected area and LSPR of the modeled nanostars to synthesized nanostars, the volume, surface area, and number of tips can be approximated without a lengthy characterization process. Knowing the nanoparticle geometry can determine drug carrier capacity, an approximate number of hot spots for EM imaging, and how the particle will interact with cells. The geometric data obtained will drive the biological application and increase the usability of this particle class

BFACF-style algorithms for polygons in the body-centered and face-centered cubic lattices

In this paper the elementary moves of the BFACF-algorithm for lattice polygons are generalised to elementary moves of BFACF-style algorithms for lattice polygons in the body-centred (BCC) and face-centred (FCC) cubic lattices. We prove that the ergodicity classes of these new elementary moves coincide with the knot types of unrooted polygons in the BCC and FCC lattices and so expand a similar result for the cubic lattice. Implementations of these algorithms for knotted polygons using the GAS algorithm produce estimates of the minimal length of knotted polygons in the BCC and FCC lattices

Catalysis by metallic nanoparticles in solution: thermosensitive microgels as nanoreactors

Metallic nanoparticles have been used as catalysts for various reactions, and the huge literature on the subject is hard to overlook. In many applications, the nanoparticles must be affixed to a colloidal carrier for easy handling during catalysis. These "passive carriers" (e.g. dendrimers) serve for a controlled synthesis of the nanoparticles and prevent coagulation during catalysis. Recently, hybrids from nanoparticles and polymers have been developed that allow us to change the catalytic activity of the nanoparticles by external triggers. In particular, single nanoparticles embedded in a thermosensitive network made from poly(N-isopropylacrylamide) (PNIPAM) have become the most-studied examples of such hybrids: immersed in cold water, the PNIPAM network is hydrophilic and fully swollen. In this state, hydrophilic substrates can diffuse easily through the network, and react at the surface of the nanoparticles. Above the volume transition located at 32°C, the network becomes hydrophobic and shrinks. Now hydrophobic substrates will preferably diffuse through the network and react with other substrates in the reaction catalyzed by the enclosed nanoparticle. Such "active carriers", may thus be viewed as true nanoreactors that open new ways for the use of nanoparticles in catalysis. In this review, we give a survey on recent work done on these hybrids and their application in catalysis. The aim of this review is threefold: we first review hybrid systems composed of nanoparticles and thermosensitive networks and compare these "active carriers" to other colloidal and polymeric carriers (e.g. dendrimers). In a second step we discuss the model reactions used to obtain precise kinetic data on the catalytic activity of nanoparticles in various carriers and environments. These kinetic data allow us to present a fully quantitative comparison of different nanoreactors. In a final section we shall present the salient points of recent efforts in the theoretical modeling of these nanoreactors. By accounting for the presence of a free-energy landscape for the reactants' diffusive approach towards the catalytic nanoparticle, arising from solvent-reactant and polymeric shell-reactant interactions, these models are capable of explaining the emergence of all the important features observed so far in studies of nanoreactors. The present survey also suggests that such models may be used for the design of future carrier systems adapted to a given reaction and solvent