Sequential signals

Simske JS, Kim SK 1995 Sequential signaling during Caenorhabditis elegans vulval induction. Nature 375 142-146... 

Sequential signals are surprisingly widespread in chemistry, and require a large number of methods for analysis. Most data are obtained via computerised instruments such as those for NIR, HPLC or NMR, and raw information such as peak integrals, peak shifts and positions is often dependent on how the information from the computer is first processed. An appreciation of this step is essential prior to applying further multivariate methods such as pattern recognition or classification. Spectra and chromatograms are examples of series that are sequential in time or frequency. However, time series also occur very widely in other areas of chemistry, for example in the area of industrial process control and natural processes. 

Micheau, O., and Tschopp, J. (2003). Induction of TNF receptor I-mediated apoptosis via two sequential signaling complexes. Cell 114, 181-190. 

Let us look at some of the traps it is easy to fall into when making sequential signal assignments. The following examples are simple but bad versions of the D-type flip flop. The function of each should be clear without showing the associated entity ... 

As one goes to higher orders, there are many other processes that can and do occur. Some are true fifth or seventh order processes and others are cascaded events arising from the sequential actions of lower order process [135]. Many of these cascaded sources of polarization interfere with the echo and quasi-echo signal and must be handled theoretically and experimentally. 

The sequence-specific assignment, however, can be made from NOE spectra (see Figures 18.17 and 18.18b) that record signals from H atoms that are close together in space. In addition to the interactions between H atoms that are far apart in the sequence, these spectra also record interactions between H atoms from sequentially adjacent residues, specifically, interactions from the H atom attached to the main chain N of residue number i -r 1 to H atoms bonded to N, Ca, and Cp of residue number i (Figure 18.19a). 

The use of a catalyst with oxidase enzyme is an example of the use of a combined enzyme system, which illustrates the wide potential offered by multi-enzyme electrode systems. Various enzymes can be arranged to work sequentially to transform quite complex substances and eventually produce a measurable concentration-dependent change, which is detected by the output signal and recorded for analysis. 

GPI anchoring is a posttranslational modification occurring in the endoplasmic reticulum where preassembled GPI anchor precursors are transferred to proteins bearing a C-terminal GPI signal sequence. The GPI anchor precursors are synthesized in the endoplasmic reticulum by sequential addition of sugar and other components to phosphatidylinositol. Protein GPI anchors are ubiquitous in eukaryotic cells. In mammalian cells, GPI anchored proteins are often found in lipid rafts which are subdomains of the plasma membrane, containing various signaling components. 

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