The Crystallography Open Database (COD), which is a project that aims to gather all available inorganic, metal-organic and small organic molecule structural data in one database, is described. The database adopts an openaccess model. The COD currently contains 80 000 entries in crystallographic information file format, with nearly full coverage of the International Union of Crystallography publications, and is growing in size and quality.

Using an open-access distribution model, the Crystallography Open Database (COD, http://www.crystallography.net) collects all known ‘small molecule / small to medium sized unit cell’ crystal structures and makes them available freely on the Internet. As of today, the COD has aggregated ∼150 000 structures, offering basic search capabilities and the possibility to download the whole database, or parts thereof using a variety of standard open communication protocols. A newly developed website provides capabilities for all registered users to deposit published and so far unpublished structures as personal communications or pre-publication depositions. Such a setup enables extension of the COD database by many users simultaneously. This increases the possibilities for growth of the COD database, and is the first step towards establishing a world wide Internet-based collaborative platform dedicated to the collection and curation of structural knowledge.

The cellular and subcellular localization of endogenous nitric oxide (NO . ) in leaves from young and senescent pea (Pisum sativum) plants was studied. Confocal laser scanning microscopy analysis of pea leaf sections with the fluorescent probe 4,5-diaminofluorescein diacetate revealed that endogenous NO. was mainly present in vascular tissues (xylem and phloem).Green fluorescence spots were also detected in the epidermal cells, palisade and spongy mesophyll cells, and guard cells. ) is a widespread intracellular and intercellular messenger with a broad spectrum of regulatory functions in many physiological processes (Moncada et al., 1991;Ignarro, 2002;Wendehenne et al., 2001;Lamattina et al., 2003;Neill et al., 2003;del Río et al., 2004). In recent years, NO. was reported to be involved in many key physiological processes of plants, such as ethylene emission (Leshem and Haramaty, 1996), response to drought (Leshem, 1996), disease resistance (Delledonne et al., 1998(Delledonne et al., , 2001Durner et al., 1998;Clarke et al., 2000), growth and cell proliferation (Ribeiro et al., 1999), maturation and senescence (Leshem et al., 1998), apoptosis/programmed cell death (Magalhaes et al., 1999;Clarke et al., 2000;Pedroso and Durzan, 2000;Pedroso et al., 2000a;Zhang et al., 2003), and stomatal closure Lamattina, 2001, 2002;Neill et al., 2002a;García-Mata et al., 2003).The application of exogenous NO . to plants has been used as a tool to study how this molecule affects some physiological processes, such as inhibition of certain enzyme activities (Clark et al., 2000;Navarre et al., 2000), cell wall lignification (Ferrer and Ros Barceló , 1999) In animal systems, a considerable attention is being dedicated to this molecule and the enzyme responsible for its production from L-Arg, nitric oxide synthase (NOS; EC 1.14. 13.39;Hemmens and Mayer, 1998; Alderton et al., 2001). On the contrary, in plants comparatively much less is known on the source of NO . production (Neill et al., 2003;Wendehenne et al., 2003;del Río et al., 2004 Article, publication date, and citation information can be found at www.plantphysiol.org/cgi