Diffusion, Crowding & Protein Stability in a Dynamic Molecular Model of the Bacterial Cytoplasm

A longstanding question in molecular biology is the extent to which the behavior of macromolecules observed in vitro accurately reflects their behavior in vivo. A number of sophisticated experimental techniques now allow the behavior of individual types of macromolecule to be studied directly in vivo; none, however, allow a wide range of molecule types to be observed simultaneously. In order to tackle this issue we have adopted a computational perspective, and, having selected the model prokaryote Escherichia coli as a test system, have assembled an atomically detailed model of its cytoplasmic environment that includes 50 of the most abundant types of macromolecules at experimentally measured concentrations. Brownian dynamics (BD) simulations of the cytoplasm model have been calibrated to reproduce the translational diffusion coefficients of Green Fluorescent Protein (GFP) observed in vivo, and “snapshots” of the simulation trajectories have been used to compute the cytoplasm's effects on the thermodynamics of protein folding, association and aggregation events. The simulation model successfully describes the relative thermodynamic stabilities of proteins measured in E. coli, and shows that effects additional to the commonly cited “crowding” effect must be included in attempts to understand macromolecular behavior in vivo

Person-to-Person Electronic Funds Transfers: Recent Developments and Policy Issues

The paper investigates the reasons why person-to-person electronic funds transfers are still not very common in the United States compared with practices in many other countries. The paper also describes recent enhancements to online and mobile banking that provide account holders with low-cost interfaces to manage person-to-person electronic funds transfers via automated clearing house (ACH). On the theoretical side, the paper characterizes the critical mass levels needed for payment instruments to become widely adopted. Given the Fed's long-term heavy involvement in check clearing, the paper concludes with policy discussions of whether intervention is needed

Monetary Policy News and Exchange Rate Responses: Do Only Surprises Matter?

This paper shows that exchange rates respond to only the surprise component of an actual US monetary policy change and that failure to disentangle the surprise component from the actual monetary policy change can lead to an underestimation of the impact of monetary policy, or even to a false acceptance of the hypothesis that monetary policy has no impact on exchange rates. This finding implies that there is a need for reexamining the empirical analyses of asset price responses to macro news that do not isolate the unexpected component of news from the expected element. In addition, we add to the debate on how quickly exchange rates respond to news by showing that the exchange rates under study absorb monetary policy surprises within the same day as the news are announced

A Portfolio-Balance Approach to the Nominal Term Structure

Explanations of why changes in the relative quantities of safe debt seem to affect asset prices often appeal informally to a portfolio balance mechanism. I show how this type of effect can be incorporated in a general class of structural, arbitrage-free asset-pricing models using a numerical solution method that allows for a wide range of nonlinearities. I consider some applications in which the Treasury market is isolated, investors have mean-variance preferences, and the short-rate process is truncated at zero. Despite its simplicity, a version of this model incorporating inflation can fit longer-term yields well, and it suggests that fluctuations in Treasury supply explain a sizeable fraction of the historical time-series variation in term premia. Nonetheless, under plausible parameterizations central-bank asset purchases have a fairly small impact on the yield curve by removing duration from the market, and these effects are particularly weak when interest rates are close to their zero lower bound

On Lower-Bound Traps: A Framework for the Analysis of Monetary Policy in the 'Age' of Central Banks

We present a simple theoretical framework that integrates the notion of the natural or neutral interest rate, liquidity preference theory, and the monetary policy practice by modern central banks. We claim that this theory explains the conditions under which an economy will experience an aggregate demand deficiency problem within a modern institutional setting. Contrary to the predictions of the New Consensus View in macroeconomics, the model suggests that structural factors such as a high saving rate and, especially, a low natural rate of growth increase the chances that an economy experiences an aggregate demand deficiency. Contrary to conventional wisdom, the model predicts that a fall in the NAIRU may lead to a rise in the natural interest rate, and vice versa