Interaction of β-Sheet Folds with a Gold Surface

The adsorption of proteins on inorganic surfaces is of fundamental biological importance. Further, biomedical and nanotechnological applications increasingly use interfaces between inorganic material and polypeptides. Yet, the underlying adsorption mechanism of polypeptides on surfaces is not well understood and experimentally difficult to analyze. Therefore, we investigate here the interactions of polypeptides with a gold(111) surface using computational molecular dynamics (MD) simulations with a polarizable gold model in explicit water. Our focus in this paper is the investigation of the interaction of polypeptides with β-sheet folds. First, we concentrate on a β-sheet forming model peptide. Second, we investigate the interactions of two domains with high β-sheet content of the biologically important extracellular matrix protein fibronectin (FN). We find that adsorption occurs in a stepwise mechanism both for the model peptide and the protein. The positively charged amino acid Arg facilitates the initial contact formation between protein and gold surface. Our results suggest that an effective gold-binding surface patch is overall uncharged, but contains Arg for contact initiation. The polypeptides do not unfold on the gold surface within the simulation time. However, for the two FN domains, the relative domain-domain orientation changes. The observation of a very fast and strong adsorption indicates that in a biological matrix, no bare gold surfaces will be present. Hence, the bioactivity of gold surfaces (like bare gold nanoparticles) will critically depend on the history of particle administration and the proteins present during initial contact between gold and biological material. Further, gold particles may act as seeds for protein aggregation. Structural re-organization and protein aggregation are potentially of immunological importance

Nitric oxide, prostaglandins and angiotensin II in the regulation of renal medullary blood flow during volume expansion

© University of Navarra 2015. This document is the Published version of a Published Work that appeared in final form in Journal of Physiology and Biochemistry. To access the final edited and published work see https://doi.org/10.1007/s13105-015-0450-8Regulation of medullary blood flow (MBF) is essential in maintaining renal function and blood pressure. However, it is unknown whether outer MBF (OMBF) and papillary blood flow (PBF) are regulated independently when extracellular volume (ECV) is enhanced. The aim of this study was to determine whether OMBF and PBF are differently regulated and whether there is an interaction between nitric oxide (NO), prostaglandins (PGs) and angiotensin II (Ang II) in regulating OMBF and PBF when ECV is enhanced. To achieve these goals, OMBF and PBF were measured by laser-Doppler in volume-expanded rats treated with a cyclooxygenase inhibitor (meclofenamate, 3 mg/kg) and/or a NO synthesis inhibitor (L-nitro-arginine methyl ester (L-NAME), 3 μg/kg/min) and/or Ang II (10 ng/kg/min). OMBF was unchanged by NO or PGs synthesis inhibition but decreased by 36 % (P < 0.05) when L-NAME and meclofenamate were infused simultaneously. PBF was similarly reduced by L-NAME (12 %), meclofenamate (17 %) or L-NAME + meclofenamate (19 %). Ang II did not modify OMBF, but it led to a similar decrease (P < 0.05) in OMBF when it was administered to rats with reduced NO (32 %), PGs (36 %) or NO and PGs (37 %) synthesis. In contrast, the fall in PBF induced by Ang II (12 %) was enhanced (P < 0.05) by the simultaneous PGs (30 %) or PGs and NO (31 %) synthesis inhibition but not in L-NAME-treated rats (20 %). This study presents novel findings suggesting that blood flows to the outer medulla and renal papilla are differently regulated and showing that there is a complex interaction between NO, PGs and Ang II in regulating OMBF and PBF when ECV is enhanced

The economic integration of Spain: a change in the inflation pattern

The behavior of Spanish inflation rates at the provincial level (consumption prices) differs over the two spans of time considered in our study (1955.1-1978.6, 1978.7-2014.4). We point to a long list of institutional and economic changes, at national and international levels, as the potential factors that might have led to this new pattern. In addition to confirming the remarkable persistence shown by the Spanish inflation, the PANIC (panel analysis of non-stationarity in idiosyncratic and common components) analysis we undertake identifies a higher importance of the common component of the series in the second period studied. Besides inflation, we draw attention to a battery of economic and labor variables, mostly through regional data, and we conclude that they tend to converge as well, particularly in the case of our second period of analysis. There are several theoretical avenues whereby the geographic convergence of these variables and the observed inflation convergence could be related. We also relate the common factor in inflation obtained to some potential explanatory variables. Moreover, a relevant additional analysis, which is only feasible for the second period, is implemented by focusing on the weightings attributed to the different groups of goods and services that make up the Consumer Price Index. The outcome we obtain is straightforward: the shopping basket across Spanish provinces has tended to become more homogeneous. In summary, a variety of changes, which we regard as having increased essentially since the late 70s, with the intensification of the Spanish integration in the core of European Union, among other factors, have brought about a regime shift in inflation behavior. The Spanish experience may offer lessons for other economies that follow similar paths, for instance Latin American countries