Singularly Perturbed Monotone Systems and an Application to Double Phosphorylation Cycles

The theory of monotone dynamical systems has been found very useful in the modeling of some gene, protein, and signaling networks. In monotone systems, every net feedback loop is positive. On the other hand, negative feedback loops are important features of many systems, since they are required for adaptation and precision. This paper shows that, provided that these negative loops act at a comparatively fast time scale, the main dynamical property of (strongly) monotone systems, convergence to steady states, is still valid. An application is worked out to a double-phosphorylation ``futile cycle'' motif which plays a central role in eukaryotic cell signaling.Comment: 21 pages, 3 figures, corrected typos, references remove

Identification of a CAPA-PVK [Ixori-PVK] from single cells of the gulf Gulf Coast tick, Amblyomma maculatum

MALDI-TOF/TOF tandem mass spectrometry has been applied to determine the complete sequence of a CAPA-PVK in the Gulf Coast tick, Amblyomma maculatum. Single cell analysis allowed the identification of the amino acid sequence of Ixori-PVK (PALIPFPRV-NH2), a periviscerokinin which had previously been identified from two other ticks, Ixodes ricinus and Boophilus microplus. The identification indicates greater conservation of sequence for the CAPA-PVK/CAP2b family in ticks as compared with insects. Side-chain fragmentation experiments provided data to distinguish between Leu/Ile ambiguities. The tick CAPA peptide shows a high sequence homology with other members of the insect periviscerokinin/ CAP2b peptides, which are associated with the regulation of critical physiological processes such as diuresis. Thus, the identification of this neuropeptide will provide the experimental basis to better understand regulation of water balance in these arthropods, providing a potential opportunity to develop neuropeptide-based control strategies against these livestock pests