High-molecular-weight precursor

Up to now, the pectinolytic enzymes of E. chrysanthemi that have been detected were extracellular secreted enzymes (PelA, B, C, D, E, L, exo-Peh and PemA), periplasmic (exo-Pel), or cytoplasmic (OGL) proteins (1, 5). In contrast, PemB is an outer membrane pectinolytic enzyme. To our knowledge it is the first pectinase characterised as a membrane protein. We presented several lines of evidence showing that PemB is a lipoprotein (i) Its N-terminal sequence has the characteristics of lipoprotein signal sequences, (ii) PemB is synthesised as a high molecular weight precursor processed into a lower molecular weight mature form, (iii) Palmitate, the most prevalent fatty acid in bacterial lipoproteins (12), is incorporated into PemB. 

The choice of the appropriate catalyst system will have an impact on the potential formation of the heavy polymers and coke. Cracking the high molecular weight precursors catalytically will significantly reduce the possibility of thermally degrading these components. The zeolite activity should be optimized in combination with an active matrix selective to upgrading the heavy feed components. 

The successful synthesis of a high molecular weight precursor to polyphenylene that could be more readily converted to its corresponding conjugated polymer was reported where the prepolymer utilized ester substituents [95,96]. In a novel bacterial oxidation of benzene, a ds-cyclohexadiene diol 21 was initially prepared that was later acetylated and polymerized as shown in Scheme 26. This polymer was determined to contain approximately 90% 1,4-linkages and 10% 1,2-linkages. 

The Wessling and Zimmerman aqueous precursor route is illustrated in Scheme 38 [156]. Here, a bis(halomethyl)monomer is reacted with dimethyl-sulfide and subsequent treatment with base affords the high molecular weight precursor polyelectrolyte 31. Due to the instability of 31, polymerization must be carried out at low temperatures (<4 °C) to avoid thermal elimination of the polyelectrolyte. Precursor polymer 31 can be stored in solution with refrigeration, and its shelf life can be increased by the addition of a small amount of pyridine. Precursor polymer 31 can be processed into highly oriented, free-standing films or fibers that can subsequently be converted to PPV with the elimination of gaseous dimethylsulfide and HCl at 200 °C. 

Possible Involvement of High-molecular-weight Precursors to Cellulose. 135... 

In addition to the suggested, but not proved, role for lipid intermediates, much speculation has appeared on the possibility that there may also exist some sort of high-molecular-weight precursor to cellulose. Here again, suggestive evidence exists for such a polymer, but conclusive proof of its existence is still lacking. 

Like other proteases, cathepsins are synthesized as high molecular weight precursors that require processing for activation. Cathepsin B (CB) is a thiol-dependent protease normally found in lysosomes, and is activated by cathepsin D (CD) and matrix metahoproteinases. Activated CB can in turn activate uPA and specific metalloproteinases. Cathepsin L (CL) is similar in specificity to that of CB however, it has little activity toward small molecular substrates. Cathepsin D, like CB, is a lysosomal protease however, CD belongs to the aspartyl group of proteases. 

Murata, K., I. Iuchi and K. Yamagami. Isolation of H-SF substance, the high-molecular-weight precursors of egg envelope proteins, from the ascites accumulated in the oestrogen-treated fish, Oryzias latipes. Zygote 1 315-324, 1993. 

Concurrent with the discovery of EP, it was recognized that all the hormones of the first group are fonned biosynthetically by posttranslational processing of a high molecular weight precursor (36, 37, 38). The precursor, proopiomelanocortin, has a molecular weight of 31,000. The complete amino acid sequence of proopiomelanocortin has been deduced from the nucleotide sequence of the complimentary DNA (39). Llpotropln forms the carboxyl terminal and is preceded by the ACTH sequence. ACTH and LPH are separated by the paired basic residue sequence Lys-Arg. 

Each component of the mixture can be analyzed by the metastable spectra without previous separation. Thus the different amino acids (or simpler amines) can be determined. Under El conditions, the determination of high-molecular-weight precursors of certain fragment ions formed in the first FFR enabled Klein [229] to use the same method to demonstrate the molecular ion at 1 u of different 1,2-diacyl glycerylphos-phatidylcholines, derived from distearoyl (m/z 786.6), l-stearoyl-2-oleoyl (m/z 787.6), etc. 

Barton, K.A., Thompson, J.F., Madison, J.T., Rosenthal, R., Jarvis, N.P., and Beachy, R.N. The biosynthesis and processing of high molecular weight precursors of soybean glycinin subunits. Biol. Chem. 257(11) 6089-6095, June 1982. 

The historically-first synthetic method consists in constructing tractable, high molecular weight precursors, called polyamic acids, vAiich are imidized during the cure cycle, with loss of water, to the intractcd>le, insoluble, infusible condensation polyimides. 

Hydrophilic branched oligo(ethylene glycol)-substituted PPV derivatives, poly(2,5-bis(l,3-bis(tri-ethoxymethoxy) propan-2-yloxy)-1,4-phenyleneviny-lene) and poly(2-methoxy-5-(l,3-bis(triethoxymeth-oxy) propan - 2-yloxy) -1,4-phenylenevinylene), have been described [23]. The polymerization reaction is carried out via the dithiocarbamate precursor route. Lithium hexamethyldisilazide is used as a base in order to get high-molecular-weight precursor polymers. After the thermal conversion of the precursor polymers into the fully conjugated systems, the solubility of the polymers has been examined. 

Louwet, E, et al. 1995. A new synthetic route to a soluble high molecular weight precursor for poly(p-phenylene vinylene). Macromolecules 28 1330. 

The nuclear encoded 22 kDa heat shock protein (hsp22) of Chlamydomonas is transported into the chloroplast, where it was localized in the grana thylakoids (9) and apparently protected PSII from photoinhibition (10). In contrast to most other imported proteins, hsp22 was not detected as a high molecular weight precursor in vitro. Therefore it does not have a precursor peptide and seems not to be processed during import in vivo (8). 

Preparation of Cryogels hy Covalent Crosslinking of High Molecular Weight Precursors... 

As for the systems discussed in Sect. 2.2, the requirement of a good solubility of the high molecular weight precursors in the medium of the unfrozen liquid microphase is also important. If a decrease in the temperature and resulting freezing of the... 

High molecular weight precursors Crosslinking agent Solvent Temperature of cryotropic gelation (°C) What was done and reported References... 

High molecular weight precursors Crosslinking agent... 

Ivanov RV, Lozinsky VI, Noh SK, Han SS, Lyoo WS (2007) Preparation and characterization of polyacrylamide cryogels produced from a high-molecular-weight precursor. I. Influence of the reaction temperature and concentration of the crosslinking agent. J Appl Polym Sci... 

In the presence of radical initiators, a high molecular weight precursor (DP around 150) was obtained in less than 5 hours. In contrast to unsubstituted PCHD, the polymer was soluble in various solvents, a result which gives a great advantage over previous PCHDs. 

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