The structure of rat ADP-ribosylation factor-1 (ARF-1) complexed to GDP determined from two different crystal forms

The ARFs are a family of 21,000 Mr proteins with biological roles in constitutive secretion and activation of phospholipase D. The structure of ARF-1 complexed to GDP determined from two crystal forms reveals a topology that is similar to that of the protein p21 ras with two differences: an additional amino-terminal helix and an extra β-strand. The Mg2+ ion in ARF-1 displays a five-coordination sphere; this feature is not seen in p21 ras, due to a shift in the relative position of the DXXG motif between the two proteins. The occurrence of a dimer in one crystal form suggests that ARF-1 may dimerize during its biological function. The dimer interface involves a region of the ARF-1 molecule that is analogous to the effector domain in p21 ras and may mediate interactions with its effector

Design issues in the British Household Panel Study

The British Household Panel Study is the largest single project ever funded by the UK Economic and Social Research Council. Housed in the ESRC's Centre on Micro-social Change in Britain at the University of Essex, the BHPS will comprise an initial 5000 households and 10000 individuals. This paper introduces the Study through an overview of its coverage and some key aspects of its design. A short discussion of some of the analytic advantages of panel data is complemented by three examples of substantive research issues where panel data can assist in our understanding of micro-social change. The BHPS is discussed as an instance of a dynamic approach to social change and its overall rationale is briefly examined. The Study's six substantive research areas - household organisation and dynamics; labour market behaviour and activity; income and wealth dynamics; housing; health; and socio-economic values - are described. The remainder of the paper is concerned with three key design issues for panel studies and explains how these have been tackled on the BHPS. The issues are (1) changing populations; (2) non-sampling errors (and especially non-response and panel conditioning); and (3) sample design. The paper is accompanied by a substantial bibliography on panel design and methodology