High-molecular-weight fraction

These contaminates originate largely from the heavy (1,050-t- °F/ 566-t- °C), high-molecular weight fraction of the FCC feed. The quantity of these metals on the E-cat is determined by their levels in the feedstock and the catalyst addition rate. Essentially, all these metals in the feed are deposited on the catalyst. Most of the iron on the E-cat comes from metal scale from piping and from the fresh catalyst. 

Table 1 gives yields and molecular weights for the total polymer and for the low and high molecular weight fractions (LMWF and HMWF). Since the resolution of GPC traces into LMWF and HMWF was estimated subjectively the molecular weights for these fractions are merely indicators of trends. 

Clancy A.N., Macrides F., Singer A. and Agosta W.C. (1984). Male hamster copulatory responses to a high molecular weight fraction of vaginal discharge effects of vomeronasal organ removal. Physiol Behav 33, 653-660. 

In fact, by fractional precipitation we found that the fractions with the highest molecular weights are sterically very uniform and contain more than 97 % of cis-1,4 double bonds (Table IV). Lower molecular weight fractions, on the other hand, have relatively high trans-1,4 contents. We therefore take the view that the rate of crystallization is determined mainly by the high molecular weight fractions. 

As an alternative, a two-step Py-GC/MS technique can be applied allowing the identification of volatile diterpenoids in the first step and of the polymeric fraction in the second step [33]. The procedure involves an on-line derivatization at 250°C with TMAH, followed by the pyrolysis of the remaining high molecular weight fraction. 

Polymerizations often afford polymodal product molecular weight distributions,18 with typically a low molecular weight fraction of several hundred daltons (fraction I), an intermediate fraction of about 4,000 (fraction II) and then a high molecular weight fraction of 10s or 106 (fraction III), though the relative proportions of the fractions depend... 

VJhile histamine releasing activity is mainly associated with high molecular weight fractions, they are not necessarily the same ones responsible for antigenic or chemotactic activity, indicating the possibility that several mechanisms may be responsible for bysslnosis. 

Chromatographic purification of cross-links. The initial steps of the purification were to separate the cross-links from monomeric amino acids, followed by the separation of individual cross-links. The acid hydrolyzate of demineralized roof powder (13.0 g collagen) was separafed on a size exclusion column fo yield the high molecular weight fractions. 

Part of the high molecular weight fractions contained ninhydrin-positive compounds displaying Rf 0 on TLC-plates (BUOH/HAC/H2O), characteristic of cross-links. To remove contaminating common amino acids, the selected fractions were further purified by adsorption chromatography on cellulose. Most of the amino acids eluted with BUOH/HAC/H2O, accounting for about three quarters of the total reactivity towards ninhydrin. The amino acids eluted with BUOH/HAC/H2O displayed spots with widely varying mobilities after TLC separation with the same eluent, whereas those eluted with water showed zero and very low mobility. 

V-1 from acid and alkaline hydrolyzates, SCX-HPLC of amino acids, a mixture of purified crosslinks and hydroxylysine b purified cross-link V-2 c amino acids from an acid hydrolyzate (6 M HCl) of reduced bovine dentin retained on a phenylboronate agarose column after purification as high molecular weight fractions by repeated size exclusion chromatography d as c, alkaline hydrolyzate (2 M KOH). Injections (c, d) resulted from 18 and 52 mg collagen originally hydrolyzed, respectively. 1 = 111 (HP) 2 = V-2 3 = IV 4 = V-1-1 (DHLNL) 5 = HLNL (bovine tendon) 6 = VI (histidinoalanine ) 7 = hydroxylysine 8 = VI (lysinoalanine). 

Figure 3. Gel permeation chromatograms of PMMA exposed to increasing doses of y radiation. High molecular weight fractions elute at low elution...

The high sensitivity of the viscosity detector to the high molecular weight fractions is demonstrated in the analysis of a sample of very high molecular weight polyCmethyl methacrylate) shown in Figure 8. A shoulder at 3,000,000 molecular weight detected by the DRI becomes a peak when detected by the viscometer detector. 

All unfractionated cellulose triacetate samples and high molecular weight fractions showed a shoulder on the high molecular weight side of the GPC distribution. Material Isolated from this region was found to be highly enriched in mannose and xylose, attributed to the presence of a hemicellu-lose derivative. Cellulose triacetate from cotton linters did not show this behavior. 

The apparent difference between viscosity average (M ) and number average molecular weight (M ) for unfractionated triacetate samples and high molecular weight fractions may be attributed to the presence of hemicellulose and polydispersity effect in these materials as shown in the table in question and in Figure 3. 

The partial blocking of the GPC column with 5 x 10 A exclusion limit in both dichloromethane and H.-methylpyrrolidone may be attributed to the presence of hemicellulose in both unfractionated triacetate samples and high molecular weight fractions used in this work. The blocking of the column in question was Indicated... 

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