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Polyimide (sometimes abbreviated PI) is a polymer containing imide groups belonging to the class of high-performance plastics. With their high heat-resistance, polyimides enjoy diverse applications in roles demanding rugged organic materials, such as high temperature fuel cells , displays, and various military roles.
The anion P 2 O 4− 7 is abbreviated PP i, standing for inorganic pyrophosphate. It is formed by the hydrolysis of ATP into AMP in cells. ATP → AMP + PP i. For example, when a nucleotide is incorporated into a growing DNA or RNA strand by a polymerase, pyrophosphate (PP i) is released.
The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). [1] However, pI is also used. [2] For brevity, this article uses pI.
The density of PP is between 0.895 and 0.93 g/cm 3. Therefore, PP is the commodity plastic with the lowest density. With lower density, moldings parts with lower weight and more parts of a certain mass of plastic can be produced. Unlike polyethylene, crystalline and amorphous regions differ only slightly in their density.
At pH 1 or lower, the phosphoric acid is practically undissociated. Around pH 4.7 (mid-way between the first two pK a values) the dihydrogen phosphate ion, [H 2 PO 4] −, is practically the only species present. Around pH 9.8 (mid-way between the second and third pK a values) the monohydrogen phosphate ion, [HPO 4] 2−, is the only species ...
Two pi bonds are the maximum that can exist between a given pair of atoms. Quadruple bonds are extremely rare and can be formed only between transition metal atoms, and consist of one sigma bond, two pi bonds and one delta bond. A pi bond is weaker than a sigma bond, but the combination of pi and sigma bond is stronger than either bond by itself.
More formulas of this nature can be given, as explained by Ramanujan's theory of elliptic functions to alternative bases. Perhaps the most notable hypergeometric inversions are the following two examples, involving the Ramanujan tau function τ {\displaystyle \tau } and the Fourier coefficients j {\displaystyle \mathrm {j} } of the J-invariant ...
The hydrolysis starts with the enzyme PI 4-kinase alpha converting PI into PI 4-phosphate , which is then converted into PI (4,5) biphosphate (PI(4,5)P 2) by the enzyme PI 4-phosphate-5-kinase . PI(4,5)P 2 is then hydrolysed by phospholipase C ( PLC ) and forms the second messengers, inositol (1,4,5) triphosphate ( IP 3 ) and diacylglycerol ( DG ).