Nitric oxide adsorption on Ru(001) at 78 and 120 K: Temperature dependence on the bonding geometry

The influence of surface temperature on NO adsorption on Ru(001) between 78 and 120 K has been investigated by high-resolution electron energy-loss spectroscopy (EELS) and thermal desorption mass spectrometry. Metastable NO adsorption states were isolated at 78 K and were identified by EELS. In all cases, heating of the NO overlayer from 78 to 120 K resulted in an irreversible conversion between adsites. All the measurements were performed in an UHV system that has been described in detail previously. Experimental techniques were employed that have also been documented thoroughly

Nongovernmental Organizations and African Governments: Seeking an Effective International Legal Framework in a New Era of Heath and Development Aid

International and domestic nongovernmental organizations (NGOs) have multiplied on the African continent as both public and private donors have shifted their funding away from ineffective governments. Many African nations, including Zimbabwe and Sudan, have responded by expelling international NGOs and enacting laws that severely limit their ability to function. In most cases, NGOs are without recourse because of their precarious position in international law. Some scholars have posited that NGOs should be granted legal personality to make them full or partial subjects in international law. This Note argues that such a solution would not promote important goals NGOs advance in Africa. It would also ignore the important role that African governments must play in health and development issues. Instead, the international community should reinforce the existing international legal framework, allow NGOs to remain independent, and create mechanisms to foster communication between NGOs and host governments

Japanese Rice Protectionism: A Challenge for the Development of Agricultural Trade Laws

The Japanese government has failed to contribute meaningfully to agricultural trade negotiations. Japan’s extreme negotiation posture primarily stems from a disinclination to make concessions in its domestic rice market. It is also a result of the ability of Japan, and other developed nations, to take advantage of the rule structure outlined by the Agreement on Agriculture. Under current agricultural laws, Japan is able to maintain many domestic measures that provide support for rice farmers while also charging prohibitively high tariffs. Japan’s reluctance to limit its support for domestic rice farmers is based on the premise that rice plays a central role in Japanese culture, and without protection, the industry would collapse. What Japan has failed to realize, however, is that the bases of its arguments have little merit today. Perhaps more importantly, Japanese resistance to agricultural trade reform seriously undermines the legitimacy of the WTO

Diffusing proteins on a fluctuating membrane: Analytical theory and simulations

Using analytical calculations and computer simulations we consider both the lateral diffusion of a membrane protein and the fluctuation spectrum of the membrane in which the protein is embedded. The membrane protein interacts with the membrane shape through its spontaneous curvature and bending rigidity. The lateral motion of the protein may be viewed as diffusion in an effective potential, hence, the effective mobility is always reduced compared to the case of free diffusion. Using a rigorous path-integral approach we derive an analytical expression for the effective diffusion coefficient for small ratios of temperature and bending rigidity, which is the biologically relevant limit. Simulations show very good quantitative agreement with our analytical result. The analysis of the correlation functions contributing to the diffusion coefficient shows that the correlations between the stochastic force of the protein and the response in the membrane shape are responsible for the reduction. Our quantitative analysis of the membrane height correlation spectrum shows an influence of the protein-membrane interaction causing a distinctly altered wave-vector dependence compared to a free membrane. Furthermore, the time correlations exhibit the two relevant timescales of the system: that of membrane fluctuations and that of lateral protein diffusion with the latter typically much longer than the former. We argue that the analysis of the long-time decay of membrane height correlations can thus provide a new means to determine the effective diffusion coefficient of proteins in the membrane.Comment: 12 pages, 8 figure

Melatonin synthesis in the human pineal gland

Poster presentation: The mammalian pineal organ is a peripheral oscillator, depending on afferent information from the so-called master clock in the suprachiasmatic nuclei of the hypothalamus. One of the best studied outputs of the pineal gland is the small and hydrophobic molecule melatonin. In all vertebrates, melatonin is synthesized rhythmically with high levels at night, signalling the body the duration of the dark period. Changes or disruptions of melatonin rhythms in humans are related to a number of pathophysiological disorders, like Alzheimer's disease, seasonal affective disorder or the Smith-Magenis-Syndrome. To use melatonin in preventive or curative interferences with the human circadian system, a complete understanding of the generation of the rhythmic melatonin signal in the human pineal gland is essential. Melatonin biosynthesis is best studied in the rodent pineal gland, where the activity of the penultimate and rate-limiting enzyme, the arylalkylamine N-acetyltransferase (AA-NAT), is regulated on the transcriptional level, whereas the regulatory role of the ultimate enzymatic step, achieved by the hydroxyindole O-methyltransferase (HIOMT), is still under debate. In rodents, Aa-nat mRNA is about 100-fold elevated during the night in response to adrenergic stimulation of the cAMP-signalling pathway, with AA-NAT protein levels closely following this dynamics. In contrast, in all ungulates studied so far (cow, sheep), a post-transcriptional regulation of the AA-NAT is central to determine rhythmic melatonin synthesis. AA-NAT mRNA levels are constantly elevated, and lead to a constitutive up-regulation of AA-NAT protein, which is, however, rapidly degraded via proteasomal proteolysis during the day. AA-NAT proteolysis is only terminated upon the nocturnal increase in cAMP levels. Similar to ungulates, a post-transcriptional control of this enzyme seems evident in the pineal gland of the primate Macaca mulatta. Studies on the molecular basis of melatonin synthesis in the human being are sparse and almost exclusively based on phenomenological data, derived from non-invasive investigations. Yet the molecular mechanisms underlying the generation of the hormonal message of darkness can currently only be deciphered using autoptic material. We therefore analyzed in human post-mortem pineal tissue Aa-nat and Hiomt mRNA levels, AA-NAT and HIOMT enzyme activity, and melatonin levels for the first time simultaneously within tissue samples of the same specimen. Here presented data show the feasibility of this approach. Our results depict a clear diurnal rhythm in AA-NAT activity and melatonin content, despite constant values for Aa-nat and Hiomt mRNA, and for HIOMT activity. Notably, the here elevated AA-NAT activity during the dusk period does not correspond to a simultaneous elevation in melatonin content. It is currently unclear whether this finding may suggest a more important role of the ultimate enzyme in melatonin synthesis, the HIOMT, for rate-limiting the melatonin rhythm, as reported recently for the rodent pineal gland. Thus, our data support for the first time experimentally that post-transcriptional mechanisms are responsible for the generation of rhythmic melatonin synthesis in the human pineal gland