The role of collagen in bone apatite formation in the presence of hydroxyapatite nucleation inhibitors

Bone is a composite material in which collagen fibrils form a scaffold for a highly organized arrangement of uniaxially oriented apatite crystals. In the periodic 67¿nm cross-striated pattern of the collagen fibril, the less dense 40-nm-long gap zone has been implicated as the place where apatite crystals nucleate from an amorphous phase, and subsequently grow. This process is believed to be directed by highly acidic non-collagenous proteins, however, the role of the collagen matrix during bone apatite mineralization remains unknown. Here, combining nanometre-scale resolution cryogenic transmission electron microscopy and cryogenic electron tomography with molecular modelling, we show that collagen functions in synergy with inhibitors of hydroxyapatite nucleation to actively control mineralization. The positive net charge close to the C-terminal end of the collagen molecules promotes the infiltration of the fibrils with amorphous calcium phosphate (ACP). Furthermore, the clusters of charged amino acids, both in gap and overlap regions, form nucleation sites controlling the conversion of ACP into a parallel array of oriented apatite crystals. We developed a model describing the mechanisms through which the structure, supramolecular assembly and charge distribution of collagen can control mineralization in the presence of inhibitors of hydroxyapatite nucleatio

Financial Sector Reform and Monetary Policy in the Netherlands

Financial sector liberalization, both domestic and in cross-border transactions, was a major force behind the gradual move to indirect controls and the shift toward full reliance on exchange rate targeting in the Netherlands. This paper analyzes the different steps in this process, discusses the main arguments behind the gradual approach, and draws lessons for other countries involved in this process. The paper argues that reforms in the financial sector, liberalization of the capital account, adjustments in supervision and regulation, and modernization of monetary management are strongly interrelated and should be part of a comprehensive reform strategy.

Monetary Instruments and their Use During the Transition From a Centrally Planned to a Market Economy

This paper discusses different instruments of monetary policy, and in particular the choice between direct and indirect instruments. It identifies the main characteristics of a country’s financial system that should be considered in selecting monetary instruments, and analyzes how these characteristics should influence that selection in countries that are progressing from a state-controlled to a market economy. The characteristics of the financial system during the initial stage of the transition sometimes favor relatively direct instruments. At this stage market-based variants of direct instruments may combine the necessary effectiveness in reducing monetary expansion with the need to introduce and stimulate competition in the financial markets. During this stage indirect instruments can be developed and tested (“belt and braces” approach). In later stages, as experience is gained, these indirect instruments can gradually replace the more direct controls.

Contents

This Working Paper should not be reported as representing the views of the IMF. The views expressed in this Working Paper are those of the author(s) and do not necessarily represent those of the IMF or IMF policy. Working Papers describe research in progress by the author(s) and are published to elicit comments and to further debate. House prices in Europe have shown diverging trends, and this paper seeks to explain these differences by analyzing three groups of countries: the “fast lane”, the average performers, and the slow movers. Price movements in the first two groups are found to be driven mostly by income and trends in user costs, and housing markets in these countries seem relatively more susceptible to adverse developments in fundamentals. Real house price declines among the slow movers are harder to explain, although ample supply, low home ownership, and less complete mortgage markets are likely factors. The impact of macroeconomic, prudential and structural policies on housing markets can be large and should be a factor in policy decisions