The influence of bovine serum albumin on β-lactoglobulin denaturation, aggregation and gelation

peer-reviewedThe effect of bovine serum albumin (BSA) on the heat-induced denaturation, aggregation and subsequent acid-induced gelation of β-lactoglobulin (β-lg) was investigated in this work. Changes in the denaturation kinetics of β-lg during heating at 78 °C were determined by monitoring the disappearance of the native protein by reverse-phase chromatography. Replacing β-lg with increasing amounts of BSA, while keeping the total protein concentration constant at 5% (w/w), significantly increased the denaturation rate of β-lg from 2.57±0.30×10−3(g L−1)(1−n)s−1 to 5.07±0.72×10−3(g L−1)(1−n)s−1 (β-lg: BSA ratio of 3:1 w/w). The reaction order for β-lg was 1.40±0.09. Partial replacement of β-lg with BSA (β-lg: BSA ratio of 3:1 w/w) significantly increased the reaction order to 1.67±0.13. Heat-induced aggregates between β-lg and BSA were studied by dynamic light scattering, two-dimensional electrophoresis and size exclusion chromatography. The partial replacement of β-lg with BSA significantly changed the gelling properties of the acid-induced gels. A rapid rate of acidification resulted in a significant decrease, while a slow acidification rate resulted in a significant increase in gel strength. Size exclusion chromatography demonstrated that intermolecular disulphide bond formation occurred during both heat-induced denaturation/aggregation and subsequent acid-induced gelation. Results clearly indicate that BSA contributed to the formation of these disulphide bonds.This work was funded under the Food Institutional Research Measure (FIRM) of the National Development Plan 2000-2006. J. Kehoe is funded by the Teagasc Walsh Fellowship schem

Can Sticky Price Models Generate Volatile and Persistent Real Exchange Rates?

The central puzzle in international business cycles is that real exchange rates are volatile and persistent. The most popular story for real exchange rate fluctuations is that they are generated by monetary shocks interacting with sticky goods prices. We quantify this story and find that it can account for some of the observed properties of real exchange rates. When prices are held fixed for at least one year, risk aversion is high and preferences are separable in leisure, the model generates real exchange rates that are as volatile as in the data. The model also generates real exchange rates that are persistent, but less so than in the data. If monetary shocks are correlated across countries, then the comovements in aggregates across countries are broadly consistent with those in the data. Making asset markets incomplete or introducing sticky wages does not measurably change the results.

Accounting for the Great Depression

Economists have offered many theories for the U.S. Great Depression, but no consensus has formed on the main forces behind it. Here we describe and demonstrate a simple methodology for determining which theories are the most promising. We show that a large class of models, including models with various frictions, are equivalent to a prototype growth model with time-varying efficiency, labor, and investment wedges that, at least on face value, look like time-varying productivity, labor taxes, and investment taxes. We use U.S. data to measure these wedges, feed them back into the prototype growth model, and assess the fraction of the fluctuations in 1929?39 that they account for. We find that the efficiency and labor wedges account for essentially all of the decline and subsequent recovery. Investment wedges play, at best, a minor role. This article originally appeared in the American Economic Review. (c) American Economic Association. ; RELATED PAPER: Staff Report 328 Business Cycle AccountingDepressions

Are structural VARs with long-run restrictions useful in developing business cycle theory?

The central finding of the recent structural vector autoregression (SVAR) literature with a differenced specification of hours is that technology shocks lead to a fall in hours. Researchers have used this finding to argue that real business cycle models are unpromising. We subject this SVAR specification to a natural economic test and show that when applied to data from a multiple-shock business cycle model, the procedure incorrectly concludes that the model could not have generated the data as long as demand shocks play a nontrivial role. We also test another popular specification, which uses the level of hours, and show that with nontrivial demand shocks, it cannot distinguish between real business cycle models and sticky price models. The crux of the problem for both SVAR specifications is that available data require a VAR with a small number of lags and such a VAR is a poor approximation to the model’s VAR. ; Formerly titled: A critique of structural VARs using business cycle theory ; Originally Working paper no. 631

A critique of structural VARs using real business cycle theory

The main substantive finding of the recent structural vector autoregression literature with a differenced specification of hours (DSVAR) is that technology shocks lead to a fall in hours. Researchers have used these results to argue that business cycle models in which technology shocks lead to a rise in hours should be discarded. We evaluate the DSVAR approach by asking, is the specification derived from this approach misspecified when the data are generated by the very model the literature is trying to discard? We find that it is misspecified. Moreover, this misspecification is so great that it leads to mistaken inferences that are quantitatively large. We show that the other popular specification that uses the level of hours (LSVAR) is also misspecified. We argue that alternative state space approaches, including the business cycle accounting approach, are more fruitful techniques for guiding the development of business cycle theory.> > Replaced by Staff Report No. 364Vector autoregression ; Business cycles

New Keynesian models: not yet useful for policy analysis

In the 1970s macroeconomists often disagreed bitterly. Macroeconomists have now largely converged on method, model design, and macroeconomic policy advice. The disagreements that remain all stem from the practical implementation of the methodology. Some macroeconomists think that New Keynesian models are on the verge of being useful for quarter-to-quarter quantitative policy advice. We do not. We argue that the shocks in these models are dubiously structural and show that many of the features of the model as well as the implications due to these features are inconsistent with microeconomic evidence. These arguments lead us to conclude that New Keynesian models are not yet useful for policy analysis.

Comparing alternative representations and alternative methodologies in business cycle accounting

We make two comparisons relevant for the business cycle accounting approach. We show that in theory representing the investment wedge as a tax on investment is equivalent to representing this wedge as a tax on capital income as long as the probability distributions over this wedge in the two representations are the same. In practice, convenience dictates differing probability distributions over this wedge in the two representations. Even so, the quantitative results under the two representations are essentially identical. We also compare our methodology, the CKM methodology, to an alternative one used in Christiano and Davis (2006) as well as by us in early incarnations of the business cycle accounting approach. We argue that the CKM methodology rests on more secure theoretical foundations.> > Replaced by Staff Report No. 384Business cycles - Econometric models