Degradation technique

By reduction in the degree of polymerisation. To produce processable rubbers the original polymers are masticated with substances such as benzothiazole disulphide and tetramethylthiuram disulphide. The more severe degradation techniques to produce liquid polysulphides are mentioned below. 

Many of the aforementioned techniques are not appropriate to direct mass-spectrometric analyses of intact high-MW and heat-labile compounds. For such samples, thermal degradation techniques (analytical pyrolysis) can be performed to generate more-volatile compounds of lower molecular weight that are amenable... 

The ability to visualize spots on a 2D gel, while useful as a fingerprint, is not the same as protein identification. Protein sequencing by the Edman degradation technique is the classical means of determining... 

Figure 10.15 Solid-phase peptide sequencing procedure based on Edman degradation technique.

Wooley and Bolton recently published a paper concerning hyperbranched polycarbonates obtained by polymerization of a monomer derived from 1,1,1-tris(4 -hydroxyphenyl)ethane [99]. A degradative technique was used to determine the degree of branching, which was found to be close to 0.53. Apparent molecular weights were in the range 16-82 kDa as determined by GPC relative to linear polystyrene standards. 

The next question is which criteria are suitable to indicate unequivocally similarities or distinctions betw een lignin preparations. In practice, physical, analytical and chemical degradative techniques are used to characterize lignins. 

A Californian sponge of the Halichondriidae family contained a sulfated sesterterpene hydroquinone and five sulfated sesterterpenes. The structures of the halisulfates 1-5 (359-363) were determined by interpretation of spectral data and a structure was proposed for halisulfate 6 (364). The halisulfates are antimicrobial and antiinflammatory [318]. The absolute configuration of halisulfate 3 (361), which was also isolated from Ircinia sp. from the Philippines, has been determined by application of the chiral amide method and by chemical degradation techniques [319]. Halisulfate 7 (365) is a sesterterpene sulfate from a Coscinoderma sp. from Yap, Micronesia [320]. 

Only a few methods for the specific degradation of polysaccharides were known when an earlier article on structural polysaccharide chemistry appeared in this Series.3 The Smith degradation,4 which has become the most frequently used, had only just been introduced. Since then, a number of specific degradation techniques have been developed. In addition, there have also been some modifications and improvements to existing methods. In this article, chemical methods for specific or selective degradation of polysaccharides, and their applications in structural analysis, will be discussed. Enzymic methods, which may be of considerable value, have already been treated in this Series.5... 

In recent years, the sensitivity of the detection of free-radical-induced DNA damage has been considerably increased (for brief reviews, see Cadet and Wein-feld 1993 Cadet et al. 1997a, b, 1999b). There is often a problem with lesions that are refractory to an enzymatic excision (Dizdaroglu et al. 1978, and further examples are reported below), but it is expected that when enzymatic degradation techniques have been further developed, acid hydrolysis and its marked problems will no longer be required. 

Garcia, C., Hernandez,T., and Costa,F. (1992b). Characterization of humic acids from uncomposted and composted sewage sludge by degradative and non-degradative techniques. Bioresource Technol. 41, 53-57. 

Other sulfur-selective chemical degradation techniques (work in progress) will probably yield additional information to further resolve remaining questions with respect to structure, origin and thermal behaviour of these sulfur-rich geopolymers. 

PDMS of native LOS-I showed a [M + Na]+ ion at m/z 1823, confirming the presence of one of each of C15, C15 OH, and C25 fatty acids per molecule of LOS and fragment ions of mlz 245.6, 477.3, 706.9, 993.9, and 1282.4 supported the evidence for the structure of LOS-I, showing that the fatty acids are present on the terminal 2-O-methyl-glucose of the trehalose unit. Similarly, for the LOS from the unknown Mycobacterium, the location of the acyl functions was confirmed by using PDMS. Thus, a combination of alkylation and degradation techniques and PDMS may be used simultaneously to establish the nature and position of the acyl functions on the lipo-oligosaccharides. 

Although the isolation of the spinach leaf large subunit cDNA clone has not been reported, the major portion of the spinach leaf large subunit (54 kDa) has been sequenced by the Edmann degradation technique (B. Smith-White and J. Preiss, 1992). Since 1991, many other ADPGlc PPase... 

Hydrolysis in dilute acid under conditions which lead to the preferential rupture of aspartyl bonds may provide an excellent means for specific cleavage of polypeptides and proteins. Of all acid degradative techniques, hydrolysis in dilute acid appears to be the most specific and closely approaches the specificity of certain proteolytic enzymes. This method, however, has not been applied widely to problems on sequence analysis. Ingram and Stretton (1962) hydrolyzed a tridecapeptide from the S-chain of human hemoglobin A2 for 12 hr at 105°C in 0.25 M acetic acid. Prefer-... 

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