Chemical signals evolution

Rasmussen, L.E.L. (1999) Evolution of chemical signals in the Asian elephant, Elephas maximus behavioural and ecological influences. J. Biosci. (Bangalore) 24, 241-251. 

Penn, D. and Potts, W.K. (1998) Chemical signals and parasite-mediated sexual selection. Trends Ecol. Evolut. 13, 391-396... 

Voigt, C.C. (2005) The evolution of perfume blending and wing sacs in emballonurid bats. In R.T. Mason, M.P. LeMaster, D. Muller-Schwarze (Eds.), Chemical Signals in Vertebrates 10. Springer Press, New York, pp. 93-100... 

Houck, L.D. 1986. The evolution of salamander courtship pheromones. In D. Duvall, D. MiHler-Schwarze and R.M. Silverstein. (Eds.) Chemical Signals in Vertebrates, Vol. IV Ecology, Evolution, and Comparative Biology. Plenum Press, New York. Pp. 173-190. 

All of the long-range kairomones attractive to parasitoids that have been identified thus far are sex pheromones of the hosts. However, we are probably aware of only a small fraction of the predators and parasites that are eavesdropping on the pheromonal communications of their prey or hosts. While the evolution of individuals that are as inconspicuous as possible to their enemies is favored, it is impossible for a species to completely avoid emitting chemical signals. Thus, pheromones that are important to reproduction or other vital functions, and are good indicators of the presence of a species, are available for predators or parasitoids to exploit. 

A one-page essay in which it is suggested that evolution in plankton is driven by a watery arms race has attracted much attention (Smetacek 2001). Smetacek discusses the concept that defence of phytoplankton by mechanical protection, increased cell size, formation of spines, or production of noxious chemicals leads to the adaptation of zooplankton to these measures. This process resulted in the shape and properties of phyto- and zooplankton that we observe today. In the years following that essay several candidate molecules were discovered and intensely studied. The concept that chemical signals and defence metabolites are important factors in plankton ecology has now become widely accepted. 

Metabolites in urine or feces provide the energetically least expensive, and evolutionarily probably the original, chemical signals in vertebrates. Much of history of evolution has concerned the development by living things of responses to metabolites, sometimes their own and sometimes produced by others. Those organisms which developed satisfactory responses succeeded, and those which did not, failed. (Lucas, 1944). Interested parties, such as members of the opposite sex, can then spy and read pertinent information about sexual and dominance status, health and body condition, quality of diet, and more. For instance, female goldfish release sex pheromones in their urine that... 

Signal specialization and evolution in mammals. In Chemical Signals in Vertebrates, vol. 8, ed. R. E. Johnston, D. Muller-Schwarze, and P. W. Sorensen, pp. 1-14. New York Plenum. 

An alternative to using selective pulses in selective ID TOCSY has been proposed [52]. The frequency selection is instead accomplished by using a homonuclear ( H) chemical shift selective filter (CSSF) [53, 54]. The chemical shift filter for frequency selection consists of a non-selective 90° pulse which is set at the frequency of the selected signal, and a systematic increment of the chemical shift evolution between this pulse and the... 

In practice, the suppression of the signals from C-bound protons is not complete. In part, this arises from imperfections of the 180°(if) pulse in the delay r. If the chemical shift evolution is not refocused, pure proton terms are generated which pass the spin-lock purge pulse. Therefore, the suppression of the signals from C-bound protons is improved by applying the Excorcycle [11] phase cycle to this 180°(if) pulse [10]. To keep the phase cycle short, only the first two steps of Excorcycle can be used. The selection of the correlations is further improved by phase cycling... 

MLEV17 sequence being one of the most used sequences [23]) in such a way as to continuously refocus the chemical shift evolution of the various signals in the xy plane. Analogously to ROESY experiments, the magnetization during the spin-lock (mixing) time disappears with T p (i.e. essentially Tj, see Section 3.4). It follows that coherence transfer in the xy plane, which is built up with a sin(7T J/jt) function, also decreases with time constant p p — p[p + p p)/2 ... 

Mixing INEPT transfer ( back transfer). Assuming that 13C magnetization is still antiphase with respect to the directly bound proton, simultaneous 90° pulses on both the 1H and 13C channels will convert the antiphase 13C coherence back into antiphase 1H coherence. This signal differs from that at the end of the first 1/(2 J) delay (step lb) in that its intensity has been modulated by the chemical-shift evolution that occurred during step 2. In other words, the 13C chemical shift has been encoded within the signal. 

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