Retrogradation process

The cycloaddition reaction on the azadiene substrate is usually followed by elimination of nitrogen, hydrogen cyanide, water, amines, or other simple compounds and, as a result of this retrograde process, a new carbo- or heterocyclic system is formed (Scheme 67). The method provides a very convenient route to the synthesis of many not easily accessible compounds. In... 

Various studies have been carried out on the gelatinization and retrogradation processes of starch. Starch gelatinization was followed by pulsed H NMR by... 

Both amylose and amylopectin take part in the retrogradation process and network structure formation and up to four different steps of ordering have been postulated [30]. The first one, which takes place in a few hours, has been ascribed to gelation of the solubilized amylose in the intergranular space forming double helices structures. The second and the third one, for which days are needed, have been ascribed to chain reordering and crystallization of amylopectin. 

If bread crumb is stored for a few hours or more, the process known as staling or retrogradation occurs. In one of the first reports of the use of NIR for the study of reaction kinetics in food systems, second derivative data at 1414 and 1465 nm were used to calculate rate constants for the retrogradation process in bread [38,39]. NIR spectra were recorded using discs sampled from bread... 

Condensable Hquids also are recovered from high pressure gas reservoirs by retrograde condensation. In this process, the high pressure fluid from the reservoir produces a Hquid phase on isothermal expansion. As the pressure decreases isotherm ally the quantity of the Hquid phase increases to a maximum and then decreases to disappearance. In the production of natural gas Hquids from these high pressure wells, the well fluids are expanded to produce the optimum amount of Hquid. The Hquid phase then is separated from the gas for further processing. The gas phase is used as a raw material for one of the other recovery processes, as fuel, or is recompressed and returned to the formation. 

An aqueous dispersion of an unmodified starch containing amylose wiU gradually form an insoluble precipitate through association of linear segments. This process is called retrogradation or set-back. 

The receptor for NGF is TrkA, a 140 kDa cell surface protein that specifically binds NGF, but not other neurotrophins [5, 6, 9]. TrkA is expressed on the neuronal cell body and on neuronal processes. In its action as a target-derived trophic factor, NGF is secreted within the target organ and it then binds to TrkA receptors present on the growing neuronal process or synapse. The NGF-TrkA complex is then internalized and subsequently translocated to the cell body by retrograde axonal transport. In those cells that respond to NGF through autocrine or paracrine mechanisms, the growth factor can bind to any of the widely distributed TrkA molecules on the neuronal membrane. 

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